COVID-19 Vaccine

On December 11, 2020, the U.S. Food and Drug Administration (FDA) issued the first emergency use authorization (EUA) for a coronavirus (COVID-19) vaccine for the prevention of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in individuals 16 years of age and older ¹. The emergency use authorization (EUA) allows the Pfizer-BioNTech COVID-19 vaccine to be distributed in the U.S. However, it is your choice to receive or not receive the Pfizer-BioNTech COVID-19 Vaccine. You will not be charged for getting the vaccine. The federal government is providing the vaccine to the American public free of charge. The Moderna COVID-19 Vaccine ² for the prevention of COVID-19 in individuals 18 years and older is currently undergoing review by the Vaccines and Related Biological Products Advisory Committee. Scientists are still learning how long COVID-19 vaccines can protect people. In addition, scientists are still learning how effective the COVID-19 vaccines are against variants of the virus that causes COVID-19. Early data show the COVID-19 vaccines may work against some variants but could be less effective against others.

As with other coronaviruses, COVID-19 also known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an RNA (ribonucleic acid) virus which encodes four major structural proteins. Most vaccine candidates focus on immunization with the spike glycoprotein, which is the main target for neutralizing antibodies following infection. Neutralizing antibodies that block viral entry into host cells by preventing interaction between the spike protein and the host cell are expected to be protective.

The Pfizer-BioNTech and Moderna COVID-19 vaccines are lipid nanoparticle-formulated messenger RNA (mRNA) vaccine. They contain the genetic sequence (mRNA) for the spike protein which is found on the surface of the SARS-CoV-2 virus, wrapped in a lipid envelope (referred to as a nanoparticle) to enable it to be transported into the cells in your body. When injected, the mRNA is taken up by your cells which translate the genetic information and transcribed by your body to produce the spike protein. These are then displayed on the surface of your cell. The protein then acts as an intracellular antigen to stimulate the immune response. This stimulates your immune system to produce antibodies and activate T-cells which prepare the immune system to respond to any future exposure to the SARS-CoV-2 virus by binding to and disabling any virus encountered. As there is no whole or live virus involved, the vaccine cannot cause disease. The mRNA naturally degrades after a few days and cannot incorporate into the host genome. Data from the Pfizer-BioNTech vaccine trials undertaken in over 40,000 individuals indicate high vaccine efficacy, with no serious safety concerns observed.

The Pfizer-BioNTech COVID-19 vaccine is an unapproved vaccine that may prevent COVID-19. There is no FDA-approved vaccine to prevent COVID-19. Pfizer-BioNTech COVID-19 Vaccine is still being studied in clinical trials. In clinical trials, approximately 20,000 individuals 16 years of age and older have received at least 1 dose of the Pfizer-BioNTech COVID-19 vaccine. In an ongoing clinical trial, the Pfizer-BioNTech COVID-19 vaccine has been shown to prevent COVID-19 following 2 doses given 3 weeks apart. The duration of protection against COVID-19 is currently unknown.

Furthermore, at this time there are no data on the size of the effect of COVID-19 vaccines on transmission. Evidence is expected to accrue during the course of the vaccine programme, and until that time the Vaccines and Related Biological Products Advisory Committee is not in a position to advise vaccination solely on the basis of indirect protection. Once sufficient evidence becomes available the committee will consider options for a cocooning strategy for immunosuppressed individuals, including whether any specific vaccine is preferred in this population.

Pfizer BioNTech COVID-19 Vaccine is administered as a series of two intramuscular shots in your upper arm, three weeks apart. The available safety data to support the emergency use authorization (EUA) include 37,586 of the participants enrolled in an ongoing randomized, placebo-controlled international study, the majority of whom are U.S. participants. These participants, 18,801 of whom received the vaccine and 18,785 of whom received saline placebo, were followed for a median of two months after receiving the second dose. The most commonly reported side effects, which typically lasted several days, were pain at the injection site, tiredness, headache, muscle pain, chills, joint pain, and fever. Of note, more people experienced these side effects after the second dose than after the first dose, so it is important for vaccination providers and recipients to expect that there may be some side effects after either dose, but even more so after the second dose.

AstraZeneca COVID-19 vaccine is a viral vector vaccine which uses a weakened adenovirus as a carrier to deliver the genetic sequence for the SARS-CoV-2 spike protein. The adenovirus has been modified so that it cannot replicate in human cells and therefore cannot cause any disease. Once it has delivered the SARS-CoV-2 spike protein genetic code, the adenovirus is destroyed by your body. The genes that encode for the spike protein on the SARS-CoV-2 virus have been inserted into the adenovirus’s genetic code to make the vaccine. When the AstraZeneca COVID-19 vaccine is injected, the modified adenovirus binds to the surface of human cells and delivers the genetic code for the spike protein. The cells then process this genetic code to manufacture the spike protein. This then stimulates your immune system which reacts by producing antibodies and memory cells to the SARS-CoV-2 virus without causing disease. If the SARS-CoV-2 virus is later encountered, your immune system should be able to respond rapidly.

The Pfizer-BioNTech COVID-19 vaccine is being given to:

• some people aged 80 and over who already have a hospital appointment in the next few weeks
• people who live or work in care homes
• health care workers at high risk

The Pfizer-BioNTech COVID-19 vaccine will be offered more widely, and at other locations, as soon as possible.

The order in which people will be offered the vaccine is based on advice from the Vaccines and Related Biological Products Advisory Committee.

Scientists are still learning how the vaccines will affect the spread of COVID-19. After you’ve been fully vaccinated against COVID-19, you should keep taking precautions in public places like wearing a mask, staying 6 feet apart from others, and avoiding crowds and poorly ventilated spaces until scientists know more.

If you’ve been fully vaccinated:

• You can gather indoors with fully vaccinated people without wearing a mask.
• You can gather indoors with unvaccinated people from one other household (for example, visiting with relatives who all live together) without masks, unless any of those people or anyone they live with has an increased risk for severe illness from COVID-19.
• If you’ve been around someone who has COVID-19, you do not need to stay away from others or get tested unless you have symptoms. However, if you live in a group setting (like a correctional or detention facility or group home) and are around someone who has COVID-19, you should still stay away from others for 14 days and get tested, even if you don’t have symptoms.

For now, if you’ve been fully vaccinated:

• You should still take steps to protect yourself and others in many situations, like wearing a mask, staying at least 6 feet apart from others, and avoiding crowds and poorly ventilated spaces. Take these precautions whenever you are:
  • In public
  • Gathering with unvaccinated people from more than one other household
  • Visiting with an unvaccinated person who is at increased risk of severe illness or death from COVID-19 or who lives with a person at increased risk
• You should still avoid medium or large-sized gatherings.
• You should still delay domestic and international travel. If you do travel, you’ll still need to follow CDC requirements and recommendations.
• You should still watch out for symptoms of COVID-19, especially if you’ve been around someone who is sick. If you have symptoms of COVID-19, you should get tested and stay home and away from others.
• You will still need to follow guidance at your workplace.

Other COVID-19 vaccines in development

AstraZeneca COVID-19 vaccine uses a replication deficient chimpanzee adenovirus as a vector that encodes the full-length SARS-CoV2 spike protein ⁸. Chimpanzee adenoviruses are non-enveloped viruses, meaning that the glycoprotein antigen is not present on the surface of the vector, but is only expressed at high levels once the vector enters the target cells. Genes are inserted to render the virus replication incompetent, and to enhance immunogenicity. Once the vector is in the nucleus, mRNA encoding the spike protein is produced that then enters the cytoplasm. This leads to translation of the target protein which acts as an intracellular antigen. Headline data from vaccine trials undertaken indicate high vaccine efficacy, with no serious safety events related to the vaccine. After the Vaccines and Related Biological Products Advisory Committee has been given the opportunity to review Phase 3 data (data on vaccine safety and efficacy) on this vaccine, this statement will be updated.

Currently, there are three main types of COVID-19 vaccines that are or soon will be undergoing large-scale (Phase 3) clinical trials in the United States. Below is a description of how each type of vaccine prompts our bodies to recognize and protect us from the virus that causes COVID-19. None of these vaccines can give you COVID-19.

1. Messenger RNA (mRNA) vaccines contain material from the virus that causes COVID-19 that gives your cells instructions for how to make a harmless protein that is unique to the virus. After your cells make copies of the protein, they destroy the genetic material from the vaccine. Your body recognizes that the protein should not be there and build T-lymphocytes and B-lymphocytes that will remember how to fight the virus that causes COVID-19 if you are infected in the future.
2. Protein subunit vaccines include harmless pieces (proteins) of the virus that cause COVID-19 instead of the entire germ. Once vaccinated, your immune system recognizes that the proteins don’t belong in your body and begins making T-lymphocytes and antibodies. If you are ever infected in the future, memory cells will recognize and fight the virus.
3. Vector vaccines contain a weakened version of a live virus—a different virus than the one that causes COVID-19—that has genetic material from the virus that causes COVID-19 inserted in it (this is called a viral vector). Once the viral vector is inside your cells, the genetic material gives cells instructions to make a protein that is unique to the virus that causes COVID-19. Using these instructions, your cells make copies of the protein. This prompts your bodies to build T-lymphocytes and B-lymphocytes that will remember how to fight that virus if you are infected in the future.

COVID-19 vaccine safety and efficacy data

Table 1. COVID-19 vaccine safety and efficacy data

Vaccine	Pfizer-BioNTech (BNT162b2) 1	ModernaTX (mRNA-1273) 2		Janssen [Johnson & Johnson] (Ad26.COV2.S) 3
Type of Vaccine, Dosing	mRNA a, 2 doses with 21 days between doses	mRNA a, 2 doses with 28 days between doses		Non-replicating adenovirus vector b, single dose
Populations included in trial c	Non-pregnant persons 16 years and older (total enrolled = 43,488) Age: 21.4% of participants were >65 years of age. The median age was 51 years. Sex: 49.4% female Race/ethnicity: 81.9% White, 9.8% Black or African American, 4.4% Asian participants, and <3% from other racial groups; 26.2% of groups; 26.2% of participants were Hispanic/Latino Most frequently reported comorbid conditions: obesity, diabetes, pulmonary disease	Non-pregnant persons 18 years and older (total enrolled = 30,351) Age: 25.3% of participants were >65 years of age. The median age was 53 years. Sex: 47.4% female Race/ethnicity: 79.4% White, 9.7% Black or African American, 4.7% Asian participants, and <3% from other racial groups; 20% of participants were Hispanic/Latino Most frequently reported comorbid conditions: obesity, diabetes, pulmonary disease, cardiovascular disease		Non-pregnant persons 18 years and older (total enrolled = 43,783) Age: 20.4% of participants were >65 years of age. The median age was 53 years. Sex: 44.5% female Race/ethnicity: 62.1% White, 17.2% Black or African American, 3.5% Asian participants, and 8.3% American Indian or Alaska Native; 45.1% of participants were Hispanic/Latino Most frequently reported comorbid conditions: obesity, diabetes, pulmonary disease, cardiovascular disease
Efficacy d	All ages—95% Vaccine group = 8 cases Placebo group = 162 cases Over age 55: 93.8% 65-74 years of age: 92.9% Females: 4 cases Males: 4 cases Race/ethnicity: 7 cases in white individuals, 1 case in Asian individual No significant differences between those with or without comorbid conditions	All ages —94.1% Vaccine group = 11 cases Placebo group = 185 cases Over age 65: 86.4% Females: 4 cases Males: 7 cases Race/ethnicity: 10 cases in white individuals, 1 case in other race/ethnic groups Only four cases in the vaccine group were related to comorbid conditions		All ages—66.9% Vaccine group = 116 cases Placebo group = 348 cases Over age 65: 76.5% Females: 88 cases Males: 85 cases Race/ethnicity: 94 cases in white individuals, 37 cases in Black or African American individuals, 6 cases in Asian individuals No significant differences between those with or without comorbid conditions
Safety (adverse events) e	Local injection site reaction (pain, swelling) 1st dose: 78.6% vs 12.8% (vaccine vs placebo) 2nd dose: 73.1% vs 10.6% Systemic reaction within 7 days 1st dose: 59.1% vs 47% 2nd dose 69.9% vs 33.8% Most commonly reported adverse events after 2nd dose: injection site pain (66.1%), fatigue (59.4%), headache (51.7%), chills (35.1%), muscle pain (37.3), joint pain (21.9%), fever (15.8%) Withdrawal and death due to serious adverse events were rare and no differences were observed between groups	Local injection site reaction (pain, swelling) 1st dose: 84.2% vs 19.8% (vaccine vs placebo) 2nd dose: 88.8% vs 18.8% Systemic reaction within 7 days 1st dose: 59.4% vs 42.2% 2nd dose 79.3% vs 36.5% Most commonly reported adverse events after 2nd dose: injection site pain (88.4%), fatigue (67.6%), headache (62.8%), chills (48.3%), muscle pain (6.1), joint pain (45.2%), fever (17.4%) Withdrawal and death due to serious adverse events were rare and no differences were observed between groups		Local injection site reaction (pain, swelling) 50.2% vs 19.4% (vaccine vs placebo)Systemic reaction within 7 days 55.1% vs 35.1% (vaccine vs placebo) Most commonly reported adverse events: injection site pain (48.6%), headache (38.9%), fatigue (38.2%), myalgia (33.2%), nausea (14.2%), and fever (9.0%) Withdrawal and death due to serious adverse events were rare and no differences were observed between groups
Areas of insufficient evidence (data)			Persons with prior COVID-19 infection Children and adolescents Pregnant Individuals Individuals who are immunocompromised Efficacy in preventing infection Efficacy against long-term effects of COVID-19

Footnotes:

^a Note the mRNA vaccine platforms use a small piece of messenger RNA that serves as a blueprint for cells to make a viral protein which causes production of neutralizing antibody. This platform is not an actual virus and will not give recipient COVID-19.

^b Note the adenovirus vaccine platforms use a replication deficient adenovirus that has been modified to include a piece of double-stranded DNA that is the blueprint for the production of the SARS-CoV-2 spike protein which causes production of neutralizing antibody. These platforms do not replicate in cells and do not cause disease due to adenoviruses or COVID-19.

^c Demographic information was pulled from the source report. Note that both manufacturers have begun including persons aged 12-17 years old but these data were not included in the FDA briefing document. Pregnancy did occur in some participants in both trials, but data are insufficient to determine safety and efficacy in this population or in persons who are lactating or immunocompromised.

^d Vaccine efficacy was a measurement of confirmed COVID-19 cases in the vaccine group compared to the placebo group. CI = 95% confidence intervals. Therefore, the endpoint measured the prevention of disease and not the prevention of infection.

^d Adverse events are represented by percentages of participants reporting an event in the vaccine group.

Are the COVID-19 vaccines safe?

The FDA and CDC have determined that the Pfizer-BioNTech, Moderna, and Johnson & Johnson vaccines have met rigorous safety and effectiveness standards. No serious safety concerns or side effects were seen in the clinical trials. Over 357 million doses of COVID-19 vaccine have been given in the United States from December 14, 2020, through August 16, 2021 ⁹.

Results from vaccine safety monitoring efforts are reassuring. Some people have no side effects. Others have reported common side effects after COVID-19 vaccination, like ⁹:

• swelling, redness, and pain at injection site
• fever
• headache
• tiredness
• muscle pain
• chills
• nausea

To date, the systems in place to monitor the safety of these vaccines have found only two serious types of health problems after vaccination, both of which are rare. These are anaphylaxis and thrombosis with thrombocytopenia syndrome (TTS) after vaccination with Johnson & Johnson/Janssen COVID-19 Vaccine ⁹.

1. Deaths. Reports of death after COVID-19 vaccination are rare. More than 357 million doses of COVID-19 vaccines were administered in the United States from December 14, 2020, through August 16, 2021. During this time, the Vaccine Adverse Event Reporting System (VAERS) received 6,789 reports of death (0.0019%) among people who received a COVID-19 vaccine ¹⁰. The FDA requires healthcare providers to report any death after COVID-19 vaccination to VAERS, even if it’s unclear whether the vaccine was the cause. Reports of adverse events to VAERS following vaccination, including deaths, do not necessarily mean that a vaccine caused a health problem. A review of available clinical information, including death certificates, autopsy, and medical records, has not established a causal link to COVID-19 vaccines. However, recent reports indicate a plausible causal relationship between the Johnson & Johnson/Janssen COVID-19 Vaccine and thrombosis with thrombocytopenia syndrome (TTS), a rare and serious adverse event where blood clots with low platelets form which has caused deaths (https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-05-12/07-COVID-Shimabukuro-508.pdf).
2. Anaphylaxis: A small number of people have had a severe allergic reaction called “anaphylaxis” after vaccination, but this is rare. Anaphylaxis can occur after any vaccination. If this occurs, vaccination providers have medicines available to effectively and immediately treat the reaction. After you get a COVID-19 vaccine, you will be asked to stay for 15–30 minutes so you can be observed in case you have a severe allergic reaction and need immediate treatment.
   • Anaphylaxis after COVID-19 vaccination has occurred in approximately 2 to 5 people per million vaccinated in the United States ¹⁰.
   • If you had a severe allergic reaction also known as anaphylaxis after getting the first shot of a COVID-19 vaccine, the CDC recommends that you NOT get a second shot of that vaccine. If the reaction was after an mRNA COVID-19 vaccine (either Pfizer-BioNTech or Moderna), you should NOT get a second shot of either of these vaccines.
   • If you have a non-severe allergic reaction to a COVID-19 vaccine such as an immediate allergic reaction after getting a shot of a COVID-19 vaccine, you should NOT get a second shot of that vaccine, even if your allergic reaction was not severe enough to require emergency care ¹¹. If the reaction was after an mRNA COVID-19 vaccine (either Pfizer-BioNTech or Moderna), you should NOT get a second shot of either of these vaccines. An immediate allergic reaction happens within 4 hours of getting vaccinated and may include symptoms such as hives, swelling, and wheezing (respiratory distress). Your doctor may refer you to a specialist in allergies and immunology to provide more care or advice.
3. Thrombosis with Thrombocytopenia Syndrome (TTS) after Vaccination with Johnson & Johnson/Janssen COVID-19 Vaccination. After receiving the Johnson & Johnson/Janssen COVID-19 Vaccine, there is risk for a rare but serious adverse event called blood clots with low platelets also known as thrombosis with thrombocytopenia syndrome (TTS). Women younger than 50 years old should especially be aware of their increased risk for this rare adverse event. There are other COVID-19 vaccines available for which this risk has not been seen. This adverse event is rare, occurring at a rate of about 7 per 1 million vaccinated women between 18 and 49 years old ⁹. For women 50 years and older and men of all ages, this adverse event is even more rare.
   • As of August 11, 2021, more than 13 million doses of the Johnson & Johnson/Janssen COVID-19 vaccine have been given in the United States ¹⁰. The CDC and FDA identified 42 confirmed reports of people who got the Johnson & Johnson/Janssen COVID-19 vaccine and later developed thrombosis with thrombocytopenia syndrome (TTS). And two confirmed cases of thrombosis with thrombocytopenia syndrome (TTS) following mRNA COVID-19 vaccination (Moderna) have been reported to the Vaccine Adverse Event Reporting System (VAERS) after more than 339 million doses of mRNA COVID-19 vaccines administered in the United States. Based on available data, there is not an increased risk for thrombosis with thrombocytopenia syndrome (TTS) after mRNA COVID-19 vaccination ¹⁰.
   • For three weeks after receiving the Johnson & Johnson/Janssen vaccine, you should be on the lookout for possible symptoms of a blood clot with low platelets. Seek medical care right away if you develop one or more of these symptoms:
     • Severe or persistent headaches or blurred vision
     • Shortness of breath
     • Chest pain
     • Leg swelling
     • Persistent abdominal pain
     • Easy bruising or tiny blood spots under the skin beyond the injection site
4. Cases of myocarditis (inflammation of the heart) and pericarditis (inflammation of the lining of the heart) in adolescents and young adults have been reported more often after getting the second dose than after the first dose of one of the two mRNA COVID-19 vaccines, Pfizer-BioNTech or Moderna ⁹. These reports are rare and the known and potential benefits of COVID-19 vaccination outweigh the known and potential risks, including the possible risk of myocarditis or pericarditis ⁹.
   • As of August 11, 2021, the Vaccine Adverse Event Reporting System (VAERS) has received 1,306 reports of myocarditis or pericarditis among people ages 30 and younger who received COVID-19 vaccine ¹⁰. Most cases have been reported after mRNA COVID-19 vaccination (Pfizer-BioNTech or Moderna), particularly in male adolescents and young adults. Through follow-up, including medical record reviews, the CDC and FDA have confirmed 762 reports of myocarditis or pericarditis. The CDC and its partners are investigating these reports to assess whether there is a relationship to COVID-19 vaccination ¹⁰.
5. Guillain-Barré syndrome (GBS) is a rare disorder where the body’s immune system damages nerve cells, causing muscle weakness and sometimes paralysis. The CDC and FDA are monitoring reports of Guillain-Barré Syndrome (GBS) in people who have received the Johnson & Johnson/Janssen COVID-19 Vaccine ¹⁰. Guillain-Barré syndrome is a rare disorder where the body’s immune system damages nerve cells, causing muscle weakness and sometimes paralysis. Most people fully recover from Guillain-Barré syndrome, but some have permanent nerve damage. After more than 13 million J&J/Janssen COVID-19 Vaccine doses administered, there have been around 161 preliminary reports of Guillain-Barré syndrome identified in the Vaccine Adverse Event Reporting System (VAERS) as of August 11, 2021 ¹⁰. These cases have largely been reported about 2 weeks after vaccination and mostly in men, many 50 years and older. The CDC will continue to monitor for and evaluate reports of Guillain-Barré syndrome occurring after COVID-19 vaccination and will share more information as it becomes available.
6. “COVID arm” is when you get a rash on the arm where you got the COVID-19 shot. The CDC has learned of reports that some people have experienced a red, itchy, swollen, or painful rash where they got the shot. These rashes are also known as “COVID arm.” These rashes can start a few days to more than a week after the first shot and are sometimes quite large. If the rash is itchy, you can take an antihistamine ¹¹. If it is painful, you can take a pain medication like acetaminophen or a non-steroidal anti-inflammatory drug (NSAID) ¹¹.
   • If you experience “COVID arm” after getting the first shot, you should still get the second shot at the recommended interval if the vaccine you got needs a second shot ¹¹. Tell your vaccination provider that you experienced a rash or “COVID arm” after the first shot. Your vaccination provider may recommend that you get the second shot in the opposite arm.

The CDC continues to closely monitor the safety of COVID-19 vaccines. If scientists find a connection between a safety issue and a vaccine, the FDA and the vaccine manufacturer will work toward an appropriate solution to address the specific safety concern (for example, a problem with a specific lot, a manufacturing issue, or the vaccine itself).

COVID-19 vaccination and COVID-19 infection

People with prior or current COVID-19 (SARS-CoV-2) infection

Data from clinical trials indicate that the currently authorized COVID-19 vaccines can be given safely to people with evidence of a prior COVID-19 (SARS-CoV-2) infection. People should be offered vaccination regardless of history of prior symptomatic or asymptomatic COVID-19 (SARS-CoV-2) infection. Viral testing to assess for acute COVID-19 (SARS-CoV-2) infection or serologic testing to assess for prior infection is not recommended for the purposes of vaccine decision-making.

Vaccination of people with known current COVID-19 (SARS-CoV-2) infection should be deferred until the person has recovered from the acute illness (if the person had symptoms) and they have met criteria to discontinue isolation. This recommendation applies to people who experience COVID-19 (SARS-CoV-2) infection before receiving any vaccine dose and those who experience SARS-CoV-2 infection after the first dose of an mRNA vaccine but before receipt of the second dose.

While there is no recommended minimum interval between infection and vaccination, current evidence suggests that the risk of COVID-19 (SARS-CoV-2) reinfection is low in the months after initial infection but may increase with time due to waning immunity. Thus, while vaccine supply remains limited, people with recent documented acute COVID-19 (SARS-CoV-2) infection may choose to temporarily delay vaccination, if desired, recognizing that the risk of reinfection and, therefore, the need for vaccination, might increase with time following initial infection.

People who previously received passive antibody therapy

Currently, there are no data on the safety and efficacy of COVID-19 vaccines in people who received monoclonal antibodies or convalescent plasma as part of COVID-19 treatment. Based on the estimated half-life of such therapies and evidence suggesting that reinfection is uncommon in the 90 days after initial infection, vaccination should be deferred for at least 90 days. This is a precautionary measure until additional information becomes available, to avoid potential interference of the antibody therapy with vaccine-induced immune responses. This recommendation applies to people who receive passive antibody therapy before receiving any vaccine dose and to those who receive passive antibody therapy after the first dose of an mRNA vaccine but before the second dose, in which case the second dose should be deferred for at least 90 days following receipt of the antibody therapy. Receipt of passive antibody therapy in the past 90 days is not a contraindication to receipt of COVID-19 vaccine. COVID-19 vaccine doses received within 90 days after receipt of passive antibody therapy do not need to be repeated.

For people receiving antibody therapies not specific to COVID-19 treatment (e.g., intravenous immunoglobulin, RhoGAM), administration of COVID-19 vaccines either simultaneously with or at any interval before or after receipt of an antibody-containing product is unlikely to substantially impair development of a protective antibody response. Thus, there is no recommended minimum interval between antibody therapies not specific to COVID-19 treatment and COVID-19 vaccination.

Vaccinated people who subsequently develop COVID-19

For vaccinated people who subsequently experience COVID-19, prior receipt of a COVID-19 vaccine should not affect treatment decisions (including use of monoclonal antibodies, convalescent plasma, antiviral treatment, or corticosteroid administration) or timing of such treatments.

If a person is fully vaccinated (i.e., ≥2 weeks after completion of a two-dose mRNA series or single dose of Janssen [Johnson & Johnson] vaccine) and tests positive for COVID-19 (SARS-CoV-2), healthcare providers and local health departments are encouraged to request the specimen be held and to report the case to their state health department. CDC will work with the state health department to collect information about the case. In addition, information about these cases should be reported to the FDA or the CDC Vaccine Adverse Event Reporting System (VAERS). The VAERS toll-free number is 1-800-822-7967 or report online to https://vaers.hhs.gov/reportevent.html.

Vaccinating people with a known COVID-19 exposure or during COVID-19 outbreaks

COVID-19 vaccines are not currently recommended for outbreak management or for post-exposure prophylaxis to prevent SARS-CoV-2 infection in a person with a known exposure. Because the median incubation period of COVID-19 is 4–5 days, it is unlikely that a dose of COVID-19 vaccine would provide an adequate immune response within the incubation period for effective post-exposure prophylaxis.

People in the community or in outpatient settings who have had a known COVID-19 exposure should not seek vaccination until their quarantine period has ended to avoid potentially exposing healthcare personnel and others during the vaccination visit. This recommendation also applies to people with a known COVID-19 exposure before receipt of the second mRNA vaccine dose.

Residents or patients with a known COVID-19 exposure in congregate healthcare settings (e.g., long-term care facilities) or congregate non-healthcare settings (e.g., correctional and detention facilities, homeless shelters) may be vaccinated. In these settings, exposure to and transmission of COVID-19 (SARS-CoV-2) can occur repeatedly for long periods of time, and healthcare personnel and other staff are already in close contact with residents. People residing in congregate settings (healthcare and non-healthcare) who have had an exposure and are awaiting SARS-CoV-2 testing results may be vaccinated if they do not have symptoms consistent with COVID-19. Vaccinators should employ appropriate infection prevention and control procedures.

How does COVID-19 vaccine work?

The Pfizer-BioNTech COVID-19 Vaccine contains messenger RNA (mRNA), which is genetic material. The vaccine contains a small piece of the SARS-CoV-2 virus’s mRNA that instructs cells in your body to make the virus’s distinctive “spike” protein. When a person receives this vaccine, their body produces copies of the spike protein, which does not cause disease, but triggers the immune system to learn to react defensively, producing an immune response against SARS-CoV-2.

COVID-19 mRNA vaccines are given in your upper arm muscle. Once the instructions (mRNA) are inside the muscle cells, the cells use them to make the protein piece. After the protein piece is made, the cell breaks down the instructions and gets rid of them.

Next, the cell displays the protein piece on its surface. Your immune systems recognize that the “spike” protein doesn’t belong there and begin building an immune response and making antibodies, like what happens in natural infection against COVID-19.

At the end of the process, your body has learned how to protect against future infection.

To understand how COVID-19 vaccines work, it helps to first look at how your body fights illness. When germs, such as the virus that causes COVID-19, invade your body, they attack and multiply. This invasion, called an infection, is what causes illness. Your immune system uses several tools to fight infection. Blood contains red cells, which carry oxygen to tissues and organs, and white or immune cells, which fight infection. Different types of white blood cells fight infection in different ways:

• Macrophages are white blood cells that swallow up and digest germs and dead or dying cells. The macrophages leave behind parts of the invading germs called antigens. The body identifies antigens as dangerous and stimulates antibodies to attack them.
• B-lymphocytes are defensive white blood cells. They produce antibodies that attack the pieces of the virus left behind by the macrophages.
• T-lymphocytes are another type of defensive white blood cell. They attack cells in the body that have already been infected.

The first time a person is infected with the virus that causes COVID-19, it can take several days or weeks for their body to make and use all the germ-fighting tools needed to get over the infection. After the infection, the person’s immune system remembers what it learned about how to protect the body against that disease.

The body keeps a few T-lymphocytes, called memory cells, that go into action quickly if the body encounters the same virus again. When the familiar antigens are detected, B-lymphocytes produce antibodies to attack them. Experts are still learning how long these memory cells protect a person against the virus that causes COVID-19.

It typically takes a few weeks for the body to produce T-lymphocytes and B-lymphocytes after vaccination. Therefore, it is possible that a person could be infected with the virus that causes COVID-19 just before or just after vaccination and then get sick because the vaccine did not have enough time to provide protection.

Sometimes after vaccination, the process of building immunity can cause symptoms, such as fever. These symptoms are normal and are a sign that the body is building immunity.

How the COVID-19 vaccine is given?

The COVID-19 vaccine is given as an intramuscular (IM) injection into your upper arm. The Pfizer-BioNTech COVID-19 vaccine is given as 2 doses, at least 21 days apart.

There are no data available on the interchangeability of the Pfizer-BioNTech COVID-19 Vaccine with other COVID-19 vaccines to complete the vaccination series. Individuals who have received one dose of Pfizer-BioNTech COVID-19 Vaccine should receive a second dose of Pfizer-BioNTech COVID-19 Vaccine to complete the vaccination series.

In exceptional situations in which COVID-19 vaccine product given for the first dose cannot be determined or is no longer available, any available mRNA COVID-19 vaccine may be administered at a minimum interval of 28 days between doses to complete the mRNA COVID-19 vaccination series. In situations where the same mRNA vaccine product is temporarily unavailable, it is preferable to delay the 2nd dose (up to 6 weeks) to receive the same product than to receive a mixed series using a different product. If two doses of different mRNA COVID-19 vaccine products are administered in these situations (or inadvertently), no additional doses of either product are recommended at this time.

The safety and efficacy of Janssen (Johnson & Johnson) COVID-19 vaccine administered after an mRNA COVID-19 vaccine has not been established. However, in limited, exceptional situations where a patient received the first dose of an mRNA COVID-19 vaccine but is unable to complete the series with either the same or different mRNA COVID-19 vaccine (e.g., due to contraindication), a single dose of Janssen COVID-19 vaccine may be considered at a minimum interval of 28 days from the mRNA COVID-19 vaccine dose. See Contraindications and Precautions section for additional information on use of Janssen COVID-19 vaccine and additional precautions in people with a contraindication to mRNA COVID-19 vaccines. Patients who receive Janssen COVID-19 vaccine after a dose of an mRNA COVID-19 vaccine should be considered to have received a valid, single-dose Janssen vaccination—not a mixed vaccination series.

Interval between mRNA doses: The second dose of Pfizer-BioNTech and Moderna vaccines should be administered as close to the recommended interval as possible, but not earlier than recommended (i.e., 3 weeks [Pfizer-BioNTech] or 1 month [Moderna]). However, second doses administered within a grace period of 4 days earlier than the recommended date for the second dose are still considered valid. If it is not feasible to adhere to the recommended interval and a delay in vaccination is unavoidable, the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be administered up to 6 weeks (42 days) after the first dose. Currently, only limited data are available on efficacy of mRNA COVID-19 vaccines administered beyond this window.

Table 2. COVID-19 vaccine administration

Vaccine	Dose	Dose volume	Number doses/series	Interval between doses
Pfizer-BioNTech	30 µg	0.3 ml	2	3 weeks (21 days)
Moderna	100 µg	0.5 ml	2	1 month (28 days)
Janssen (Johnson & Johnson)	5×1010 viral particles	0.5 ml	1	N/A

Footnotes: A single, valid vaccination series (i.e., either a two-dose mRNA COVID-19 vaccine series or a single dose of Janssen [Johnson & Johnson] COVID-19 vaccine) should be administered. People are not recommended to receive more than one complete COVID-19 vaccination series.

COVID-19 vaccines coadministration with other vaccines

None of the currently authorized COVID-19 vaccines are live virus vaccines. Because data are lacking on the safety and efficacy of COVID-19 vaccines administered simultaneously with other vaccines, the vaccine series should routinely be administered alone, with a minimum interval of 14 days before or after administration of any other vaccine. However, COVID-19 and other vaccines may be administered within a shorter period in situations where the benefits of vaccination are deemed to outweigh the potential unknown risks of vaccine coadministration (e.g., tetanus-toxoid-containing vaccination as part of wound management, rabies vaccination for post-exposure prophylaxis, measles or hepatitis A vaccination during an outbreak) or to avoid barriers to or delays in to COVID-19 vaccination (e.g., in long-term care facility residents or healthcare personnel who received influenza or other vaccinations before or upon admission or onboarding). If COVID-19 vaccines are administered within 14 days of another vaccine, doses do not need to be repeated for either vaccine.

COVID-19 vaccines booster doses

The need for and timing for COVID-19 booster doses have not been established. No additional doses are recommended at this time.

Who should not get COVID-19 vaccine?

You should not get the Pfizer-BioNTech COVID-19 Vaccine if you:

• had a severe allergic reaction after a previous dose of this vaccine
• had a severe allergic reaction to any ingredient of this vaccine

Table 3. Triage of people presenting for COVID-19 vaccination

CONTRAINDICATION to COVID-19 vaccination	PRECAUTION to COVID-19 vaccination	MAY PROCEED with COVID-19 vaccination
History of the following: Severe allergic reaction (e.g., anaphylaxis) after a previous dose or to component of the vaccine† Immediate allergic reaction* of any severity after a previous dose or known (diagnosed) allergy to a component of the vaccine†	Among people without a contraindication, a history of: Any immediate allergic reaction* to other vaccines or injectable therapies‡ Note: people with a contraindication to mRNA COVID-19 vaccines have a precaution to Janssen COVID-19 vaccine, and vice versa. See footnote for additional information on additional measures to take in these people.#	Among people without a contraindication or precaution, a history of: Allergy to oral medications (including the oral equivalent of an injectable medication) History of food, pet, insect, venom, environmental, latex, etc., allergies Family history of allergies
Actions: Do not vaccinate. Consider referral to allergist-immunologist. Consider other vaccine alternative.†	Actions: Risk assessment Consider referral to allergist-immunologist 30-minute observation period if vaccinated	Actions: 30-minute observation period: people with history of anaphylaxis (due to any cause) 15-minute observation period: all other people

Footnotes:

† See Table 4 below for a list of ingredients. People with a contraindication to one of the mRNA COVID-19 vaccines should not receive doses of either of the mRNA vaccines (Pfizer-BioNTech or Moderna).

* Immediate allergic reaction to a vaccine or medication is defined as any hypersensitivity-related signs or symptoms consistent with urticaria, angioedema, respiratory distress (e.g., wheezing, stridor), or anaphylaxis that occur within four hours following administration.

‡ Includes people with a reaction to a vaccine or injectable therapy that contains multiple components, one of which is a vaccine component, but in whom it is unknown which component elicited the immediate allergic reaction.

# Polyethylene glycol (PEG) is an ingredient in both mRNA COVID-19 vaccines, and polysorbate 80 is an ingredient in Janssen COVID-19 vaccine. PEG and polysorbate are structurally related, and cross-reactive hypersensitivity between these compounds may occur. People with a contraindication to mRNA COVID-19 vaccines (including due to a known allergy to PEG) have a precaution to Janssen COVID-19 vaccine. Among people who received one mRNA COVID-19 dose but for whom the second dose is contraindicated, consideration may be given to vaccination with Janssen COVID-19 vaccine (administered at least 28 days after the mRNA COVID-19 dose). People with a contraindication to Janssen COVID-19 vaccine (including due to a known allergy to polysorbate) have a precaution to mRNA COVID-19 vaccines. For people with these precautions, referral to an allergist-immunologist should be considered. Healthcare providers and health departments may also request a consultation from the Clinical Immunization Safety Assessment COVIDvax project (https://www.cdc.gov/vaccinesafety/ensuringsafety/monitoring/cisa/index.html). In patients with these precautions, vaccination should only be undertaken in an appropriate setting under the supervision of a health care provider experienced in the management of severe allergic reactions.

Can I receive the COVID-19 vaccine with other vaccines?

There is no information on the use of the Pfizer-BioNTech COVID-19 Vaccine with other vaccines.

Can I receive the COVID-19 vaccine if I am pregnant or breastfeeding?

If you are pregnant or breastfeeding, discuss your options with your healthcare provider.

There are no data as yet on the safety of COVID-19 vaccines in pregnancy, either from human or animal studies. Given the lack of evidence, the Vaccines and Related Biological Products Advisory Committee favors a precautionary approach and does not currently advise COVID-19 vaccination in pregnancy.

Women should be advised not to come forward for vaccination if they may be pregnant or are planning a pregnancy within three months of the first dose.

Data are anticipated which will inform discussions on vaccination in pregnancy. The Vaccines and Related Biological Products Advisory Committee will review these as soon as they become available.

You should wait to have the COVID-19 vaccine:

• if you’re pregnant you should not be vaccinated – you should wait until you’ve had your baby
• if you’re breastfeeding – you should wait until you’ve stopped breastfeeding
• If you were breastfeeding when you had the first dose you are advised not to have the second dose until you have finished breastfeeding
• if you are planning to get pregnant in the next 3 months, you should delay your vaccination
• if you know you are not pregnant you can start the two-dose course now and you should avoid getting pregnant until at least 2 months after the second dose
• if you have had the first dose and then become pregnant you should delay the second dose until after the pregnancy is over

If you have the COVID-19 vaccine, you should not get pregnant for at least 2 months after having the 2nd dose.

If you later find out you were pregnant when you had the COVID-19 vaccine, do not worry. The vaccine cannot give you or your baby COVID-19.

There’s no evidence it’s unsafe if you’re pregnant or breastfeeding. But more evidence is needed before you can be offered the vaccine.

This advice is precautionary until additional evidence is available to support the use of this vaccine in pregnancy and breastfeeding.

Will the COVID-19 vaccine give me COVID-19?

No. The Pfizer-BioNTech COVID-19 Vaccine does not contain SARS-CoV-2 and cannot give you COVID-19. The vaccine was shown to prevent disease but hasn’t been shown to prevent infection with the virus. People who are vaccinated may be able to spread it to others.

Can I still get COVID-19 after I get the vaccine?

There is a small chance that you could still get sick if you are exposed to the virus, as the vaccines are not 100% effective. Also, if you are exposed to the virus just before or after getting the vaccine, you could get sick before the vaccine has time to work. However, the odds are greater that you won’t get sick, become seriously ill, or need to be hospitalized after receiving the vaccine.

If I’ve already had COVID-19, should I get vaccinated?

Health experts say that you should get COVID-19 vaccine even if you’ve already had COVID-19. They believe the vaccine could provide stronger immunity, even for those who have had the virus. This is because coronaviruses often do not create long-lasting natural immunity in humans.

What is Covid-19 breakthrough infection?

COVID-19 breakthrough infection is when fully vaccinated people become infected with COVID-19 (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) ¹². COVID-19 vaccines are effective at preventing most infections. However, like most vaccines, they are not 100% effective. Because vaccines are not 100% effective, as the number of people who are fully vaccinated goes up, the number of breakthrough infections will also increase.

Fully vaccinated people with a breakthrough infection are less likely to develop serious illness than those who are unvaccinated and get COVID-19 ¹². This means they are much less likely to be hospitalized or die than people who are not vaccinated. Therefore, the CDC recommends people get a COVID-19 vaccine as soon as they can to protect themselves from severe disease and death. However, people who get vaccine breakthrough infections can be contagious.

It typically takes about 2 weeks for the body to build protection after vaccination. You are fully vaccinated two weeks after your second dose of Pfizer -BioNTech or Moderna vaccine and two weeks after your single dose of Johnson & Johnson’s (Janssen) vaccine. It is possible you could still get COVID-19 soon after vaccination because your body has not had enough time to build protection. Keep taking precautions until you are fully vaccinated.

People who have a condition or are taking medications that weaken their immune system may not be fully protected even if they are fully vaccinated. They should continue to take all precautions recommended for unvaccinated people, including wearing a well-fitted mask, until advised otherwise by their healthcare provider.

What are the ingredients in the COVID-19 Vaccine?

The Pfizer BioNTech COVID-19 Vaccine includes the following ingredients ¹³: mRNA, lipids ¹⁴-2000]-N,N-ditetradecylacetamide

PEG2000-DMG: 1,2-dimyristoyl-rac-glycerol, methoxypolyethylene glycolPolysorbate-801,2-distearoyl-sn-glycero-3-phosphocholine1,2-distearoyl-sn-glycero-3-phosphocholine2-hydroxypropyl-β-cyclodextrinCholesterolCholesterolCitric acid monohydrate(4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate)SM-102: heptadecan-9-yl 8-¹⁵.

What is herd immunity?

Herd immunity occurs when a large portion of a community (the herd) becomes immune to a disease, making the spread of disease from person to person unlikely. As a result, the whole community becomes protected — not just those who are immune.

Often, a percentage of the population must be capable of getting a disease in order for it to spread. This is called a threshold proportion. If the proportion of the population that is immune to the disease is greater than this threshold, the spread of the disease will decline. This is known as the herd immunity threshold.

What percentage of a community needs to be immune in order to achieve herd immunity? It varies from disease to disease. The more contagious a disease is, the greater the proportion of the population that needs to be immune to the disease to stop its spread. For example, the measles is a highly contagious illness. It’s estimated that 94% of the population must be immune to interrupt the chain of transmission.

How is herd immunity achieved?

There are two paths to herd immunity for COVID-19 — vaccines and infection.

Vaccines

A vaccine for the virus that causes COVID-19 is an ideal approach to achieving herd immunity. Vaccines create immunity without causing illness or resulting complications. Herd immunity makes it possible to protect the population from a disease, including those who can’t be vaccinated, such as newborns or those who have compromised immune systems. Using the concept of herd immunity, vaccines have successfully controlled deadly contagious diseases such as smallpox, polio, diphtheria, rubella and many others.

Reaching herd immunity through vaccination sometimes has drawbacks, though. Protection from some vaccines can wane over time, requiring revaccination. Sometimes people don’t get all of the shots that they need to be completely protected from a disease.

In addition, some people may object to vaccines because of religious objections, fears about the possible risks or skepticism about the benefits. People who object to vaccines often live in the same neighborhoods or attend the same religious services or schools. If the proportion of vaccinated people in a community falls below the herd immunity threshold, exposure to a contagious disease could result in the disease quickly spreading. Measles has recently resurged in several parts of the world with relatively low vaccination rates, including the United States. Opposition to vaccines can pose a real challenge to herd immunity.

Natural infection

Herd immunity can also be reached when a sufficient number of people in the population have recovered from a disease and have developed antibodies against future infection. For example, those who survived the 1918 flu (influenza) pandemic were later immune to infection with the H1N1 flu, a subtype of influenza A. During the 2009-10 flu season, H1N1 caused the respiratory infection in humans that was commonly referred to as swine flu.

However, there are some major problems with relying on community infection to create herd immunity to the virus that causes COVID-19. First, it isn’t yet clear if infection with the COVID-19 virus makes a person immune to future infection.

Research suggests that after infection with some coronaviruses, reinfection with the same virus — though usually mild and only happening in a fraction of people — is possible after a period of months or years. Further research is needed to determine the protective effect of antibodies to the virus in those who have been infected.

Even if infection with the COVID-19 virus creates long-lasting immunity, a large number of people would have to become infected to reach the herd immunity threshold. Experts estimate that in the U.S., 70% of the population — more than 200 million people — would have to recover from COVID-19 to halt the epidemic. If many people become sick with COVID-19 at once, the health care system could quickly become overwhelmed. This amount of infection could also lead to serious complications and millions of deaths, especially among older people and those who have chronic conditions.

Interpretation of COVID-19 test results in vaccinated people

Prior receipt of a COVID-19 vaccine will not affect the results of SARS-CoV-2 viral tests (nucleic acid amplification or antigen tests). Currently available antibody tests for SARS-CoV-2 assess IgM and/or IgG to one of two viral proteins: spike or nucleocapsid. Because COVID-19 vaccines are constructed to encode the spike protein, a positive test for spike protein IgM/IgG could indicate prior infection and/or vaccination. To evaluate for evidence of prior infection in an individual with a history of COVID-19 vaccination, a test that specifically evaluates IgM/IgG to the nucleocapsid protein should be used.

Antibody testing is not currently recommended to assess for immunity to SARS-CoV-2 following COVID-19 vaccination because the clinical utility of post-vaccination testing has not been established. Antibody tests currently authorized under an EUA have variable sensitivity, specificity, as well as positive and negative predictive values, and are not authorized for the assessment of immune response in vaccinated people. Furthermore, the serologic correlates of protection have not been established, and antibody testing does not evaluate the cellular immune response, which may also play a role in vaccine-mediated protection. Finally, antibody testing against nucleocapsid will not detect immune responses resulting from vaccination, but patients may not always know what type of antibody test was used. If antibody testing was performed following vaccination, additional doses of the same or different COVID-19 vaccines are not recommended based on antibody test results at this time. If antibody testing was done after the first dose of an mRNA vaccine, the vaccination series should be completed regardless of the antibody test result.

What is emergency use authorization (EUA)?

The United States FDA has made COVID-19 vaccines available under an emergency access mechanism called an EUA. The EUA is supported by a Secretary of Health and Human Services (HHS) declaration that circumstances exist to justify the emergency use of drugs and biological products during the COVID-19 pandemic. To date, no COVID-19 vaccine candidates have been approved (licensed) by the FDA. The FDA issued emergency use authorizations (EUA) for three vaccines. EUAs were given for mRNA vaccines from Pfizer/BioNTech and Moderna in December 2020. The third EUA was issued on February 27, 2021 for the Janssen (Johnson & Johnson) COVID-19 vaccine, which uses a non-replicating adenovirus vector. The COVID-19 vaccines have not undergone the same type of review as an FDA-approved or cleared product. FDA may issue an EUA when certain criteria are met, which includes that there are no adequate, approved, and available alternatives. In addition, the FDA decision is based on the totality of scientific evidence available showing that the product may be effective to prevent COVID-19 during the COVID-19 pandemic and that the known and potential benefits of the product outweigh the known and potential risks of the product. All of these criteria must be met to allow for the product to be used during the COVID-19 pandemic.

The EUA for the COVID-19 vaccines is in effect for the duration of the COVID-19 declaration justifying emergency use of these products, unless terminated or revoked (after which the products may no longer be used).

When can I get a COVID-19 vaccine booster?

Not immediately. COVID-19 constantly evolves. Experts are looking at all available data to understand how well COVID-19 vaccines are working, including how new variants, like Delta variant, affect vaccine effectiveness. If the U.S. Food and Drug Administration (FDA) authorizes and the CDC’s Advisory Committee on Immunization Practices (ACIP) recommends it, the goal is for people to start receiving a COVID-19 booster shot this fall, with individuals being eligible starting 8 months after they received their second dose of an mRNA vaccine (either Pfizer-BioNTech or Moderna). The FDA is conducting an independent evaluation to determine the safety and effectiveness of a booster dose of the mRNA vaccines. ACIP will decide whether to issue a booster dose recommendation based on a thorough review of the evidence.

Who will be the first people to get a booster dose?

If FDA authorizes and the CDC’s Advisory Committee on Immunization Practices (ACIP) recommends a booster dose, the goal is for the first people eligible for a booster dose to be those who were the first to receive a COVID-19 vaccination (those who are most at risk). This includes healthcare providers, residents of long-term care facilities, and other older adults.

What’s the difference between a booster dose and an additional dose?

Sometimes people who are moderately to severely immunocompromised do not build enough (or any) protection when they first get a vaccination. When this happens, getting another dose of the same vaccine can sometimes help them build more protection against the disease. This appears to be the case for some immunocompromised people and COVID-19 vaccines. The CDC recommends moderately to severely immunocompromised people consider receiving an additional (third) dose of an mRNA COVID-19 vaccine (Pfizer-BioNTech or Moderna) at least 28 days after the completion of the initial 2-dose mRNA COVID-19 vaccine series.

In contrast, a “booster dose” refers to another dose of a vaccine that is given to someone who built enough protection after vaccination, but then that protection decreased over time (this is called waning immunity). The U.S. Department of Health and Human Services (HHS) has developed a plan to begin offering COVID-19 booster shots to people this fall. Implementation of the plan is subject to FDA’s authorization and ACIP’s recommendation.

If I need a booster dose, does that mean that the vaccines aren’t working?

No. COVID-19 vaccines are working very well to prevent severe illness, hospitalization, and death, even against the widely circulating Delta variant. However, with the Delta variant, public health experts are starting to see reduced protection against mild and moderate disease. For that reason, the U.S. Department of Health and Human Services (HHS) is planning for a booster shot so vaccinated people maintain protection over the coming months.

Will people who received Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 vaccine need a booster shot?

It is likely that people who received a J&J COVID-19 vaccine will need a booster dose. Because the J&J/Janssen vaccine wasn’t given in the United States until 70 days after the first mRNA vaccine doses (Pfizer-BioNTech and Moderna), the data needed to make this decision aren’t available yet. These data are expected in the coming weeks. With those data in hand, CDC will keep the public informed with a timely plan for J&J/Janssen booster shots.

Can people who received Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 vaccine get a booster dose of an mRNA vaccine?

No, there aren’t enough data currently to support getting an mRNA vaccine dose (either Pfizer-BioNTech or Moderna) if someone has gotten a J&J/Janssen vaccine. People who got the J&J/Janssen vaccine will likely need a booster dose, and more data are expected in the coming weeks. With those data in hand, CDC will keep the public informed with a timely plan for J&J/Janssen booster shots.

Who is at risk for coronavirus (COVID-19) infections?

Coronavirus (COVID-19) can make anyone seriously ill. But for some people, the risk is higher.

There are 2 levels of higher risk:

1. People at high risk (clinically extremely vulnerable)
2. People at moderate risk (clinically vulnerable)

People at high risk (clinically extremely vulnerable)

You may be at high risk from coronavirus (COVID-19) if you:

• have had an organ transplant
• are having chemotherapy or antibody treatment for cancer, including immunotherapy
• are having an intense course of radiotherapy (radical radiotherapy) for lung cancer
• are having targeted cancer treatments that can affect the immune system (such as protein kinase inhibitors or PARP inhibitors)
• have blood or bone marrow cancer (such as leukemia, lymphoma or myeloma)
• have had a bone marrow or stem cell transplant in the past 6 months, or are still taking immunosuppressant medicine
• have been told by a doctor you have a severe lung condition (such as cystic fibrosis, severe asthma or severe chronic obstructive pulmonary disease [COPD])
• have a condition that means you have a very high risk of getting infections (such as severe combined immunodeficiency [SCID] or sickle cell)
• are taking medicine that makes you much more likely to get infections (such as high doses of steroids or immunosuppressant medicine)
• have a serious heart condition and are pregnant
• have a problem with your spleen or your spleen has been removed (splenectomy)
• are an adult with Down’s syndrome
• are an adult who is having dialysis or has severe (stage 5) long-term kidney disease
• have been classed as clinically extremely vulnerable, based on clinical judgement and an assessment of your needs

People at moderate risk (clinically vulnerable)

People at moderate risk from coronavirus (COVID-19) include people who:

• are 70 or older
• have a lung condition that’s not severe (such as asthma, COPD, emphysema or bronchitis)
• have heart disease (such as heart failure)
• have diabetes
• have chronic kidney disease
• have liver disease (such as hepatitis)
• have a condition affecting the brain or nerves (such as Parkinson’s disease, motor neurone disease, multiple sclerosis or cerebral palsy)
• have a condition that means they have a high risk of getting infections
• are taking medicine that can affect the immune system (such as low doses of steroids)
• are very obese (a BMI of 40 or above)
• are pregnant

If you’re at high risk (clinically extremely vulnerable) from coronavirus (COVID-19), there are things you can do to help keep yourself safe.

DO

• try to stay at least 2 meters (3 steps) away from anyone you do not live with (or anyone not in your support bubble)
• wash your hands with soap and water often – do this for at least 20 seconds
• use hand sanitizer gel if soap and water are not available
• wash your hands as soon as you get home
• wear something that covers your nose and mouth in places where it’s hard to stay away from other people, such as on public transport, in shops and in hospitals

Work

• You should work from home if possible. Your employer should support you to do this.
• If you cannot work from home and you’re concerned about having to go to work, talk to your employer. Employers should make sure suitable arrangements are in place so you can go to work.

Shopping

To reduce your risk from coronavirus (COVID-19), you may want to:

• do your shopping online
• ask family or friends to collect shopping for you
• avoid busy times if you go shopping.

Who can get the COVID-19 vaccine?

Current evidence strongly indicates that the single greatest risk of mortality from COVID-19 is increasing age and that the risk increases exponentially with age ¹⁶. Mathematical modelling indicates that the optimal strategy for minimizing future deaths or quality adjusted life year (QALY) losses is to offer vaccination to older age groups first. These models assume an available vaccine is both safe and effective in older adults ¹⁷. Data also indicate that the absolute risk of mortality is higher in those over 65 years than that seen in the majority of younger adults with an underlying health condition (see above). Accordingly, the Vaccines and Related Biological Products Advisory Committee’s advice largely prioritizes based on age.

Age-based programmes are usually easier to implement and therefore achieve higher vaccine uptake. An age-based programme is also likely to increase uptake in those with clinical risk factors as the prevalence of these increases with age.

The Vaccines and Related Biological Products Advisory Committee’s advice is to offer vaccination to those aged 65 years and over followed by those in clinical risk groups aged 16 years and over.

The risk groups identified by the committee are set out below:

• chronic respiratory disease, including chronic obstructive pulmonary disease (COPD), cystic fibrosis and severe asthma
• chronic heart disease (and vascular disease)
• chronic kidney disease
• chronic liver disease
• chronic neurological disease including epilepsy
• Down’s syndrome
• severe and profound learning disability
• diabetes
• solid organ, bone marrow and stem cell transplant recipients
• people with specific cancers
• immunosuppression due to disease or treatment
• asplenia and splenic dysfunction
• morbid obesity
• severe mental illness

Many individuals who are clinically extremely vulnerable will have some degree of immunosuppression or be immunocompromised and may not respond as well to the vaccine. Therefore, those who are clinically extremely vulnerable should continue to follow government advice on reducing their risk of infection. Consideration has been given to vaccination of household contacts of immunosuppressed individuals.

Older adults resident in care homes

There is clear evidence that those living in residential care homes for older adults have been disproportionately affected by COVID-19 ¹⁸ as they have had a high risk of exposure to infection and are at higher clinical risk of severe disease and mortality. Given the increased risk of outbreaks, morbidity and mortality in these closed settings, these adults are considered to be at very high risk. The committee’s advice is that this group should be the highest priority for vaccination. Vaccination of residents and staff at the same time is considered to be a highly efficient strategy within a mass vaccination programme with the greatest potential impact.

The order of priority for each group in the population corresponds with data on the number of individuals who would need to be vaccinated to prevent one death, estimated from UK data obtained from March to June 2020 ¹⁶.

This priority list is as follows:

1. residents in a care home for older adults and their carers
2. all those 80 years of age and over and frontline health and social care workers
3. all those 75 years of age and over
4. all those 70 years of age and over and clinically extremely vulnerable individuals
5. all those 65 years of age and over
6. all individuals aged 16 years to 64 years with underlying health conditions which put them at higher risk of serious disease and mortality
7. all those 60 years of age and over
8. all those 55 years of age and over
9. all those 50 years of age and over

It is estimated that taken together, these groups represent around 99% of preventable mortality from COVID-19.

The vaccine advisory committee advises that implementation of the COVID-19 vaccine programme should aim to achieve high vaccine uptake. An age-based programme will likely result in faster delivery and better uptake in those at the highest risk.

Health and social care workers

Frontline health and social care workers are at increased personal risk of exposure to infection with COVID-19 and of transmitting that infection to susceptible and vulnerable patients in health and social care settings. The committee considers frontline health and social care workers who provide care to vulnerable people a high priority for vaccination. Protecting them protects the health and social care service and recognizes the risks that they face in this service. Even a small reduction in transmission arising from vaccination would add to the benefits of vaccinating this population, by reducing transmission from health and social care workers to multiple vulnerable patients and other staff members. This group includes those working in hospice care and those working temporarily in the COVID-19 vaccination programme who provide face-to-face clinical care.

There is evidence that infection rates are higher in residential care home staff ¹⁹, than in those providing domiciliary care or in healthcare workers. Care home workers are therefore considered a very high priority for vaccination.

Prioritization amongst health and social care workers

Frontline health and social care workers at high risk of acquiring infection, at high individual risk of developing serious disease, or at risk of transmitting infection to multiple vulnerable persons or other staff in a healthcare environment, are considered of higher priority for vaccination than those at lower risk. This prioritization should be taken into account during vaccine deployment.

COVID-19 vaccination of people with certain underlying medical conditions

Any currently authorized COVID-19 vaccine can be administered to people with underlying medical conditions who have no contraindications to vaccination; the Advisory Committee on Immunization Practices (ACIP) does not state a product preference. Clinical trials demonstrated similar safety and efficacy profiles in people with some underlying medical conditions, including those that place them at increased risk for severe COVID-19, compared to people without comorbidities. Additional information for people with specific underlying medical conditions is included below.

Immunocompromised people

People with HIV infection or other immunocompromising conditions or people who take immunosuppressive medications or therapies might be at increased risk for severe COVID-19. No data are available to establish COVID-19 vaccine safety and efficacy in these groups. However, the currently authorized COVID-19 vaccines are not live vaccines and therefore can be safely administered to immunocompromised people. People with stable HIV infection were included in the COVID-19 vaccine clinical trials, though data remain limited.

Immunocompromised people can receive COVID-19 vaccination. Data are currently insufficient to inform optimal timing of COVID-19 vaccination among people who are planning to receive immunosuppressive therapies. However, based on general best practices for vaccination of immunocompromised people, ideally COVID-19 vaccination should be completed at least two weeks before initiation of immunosuppressive therapies. When it is not possible to administer a complete COVID-19 vaccine series (i.e., two doses of an mRNA vaccine or a single dose of Janssen COVID-19 vaccine) in advance, people on immunosuppressive therapy can still receive COVID-19 vaccination. Decisions to delay immunosuppressive therapy to complete COVID-19 vaccination should consider the person’s risks related to their underlying condition.

Antibody testing is not recommended to assess for immunity to COVID-19 (SARS-CoV-2) following COVID-19 vaccination. At this time, revaccination is not recommended after people who received COVID-19 vaccines during chemotherapy or treatment with other immunosuppressive drugs regain immune competence. Recommendations on re-vaccination or additional doses of COVID-19 vaccines may be updated when additional information is available.

People should be counseled about the unknown vaccine safety profile and effectiveness in immunocompromised populations, the potential for reduced immune responses, and the need to continue to follow current guidance to protect themselves against COVID-19.

People with autoimmune conditions

No data are available on the safety and efficacy of COVID-19 vaccines in people with autoimmune conditions, though these people were eligible for enrollment in mRNA COVID-19 vaccine clinical trials. No imbalances were observed in the occurrence of symptoms consistent with autoimmune conditions or inflammatory disorders in clinical trial participants who received COVID-19 vaccine compared to placebo. People with autoimmune conditions may receive any authorized COVID-19 vaccine.

People with a history of Guillain-Barré syndrome

No cases of Guillain-Barré syndrome (GBS) were reported following vaccination among participants in the mRNA COVID-19 vaccine clinical trials. One case of Guillain-Barré syndrome was reported in a participant in the vaccine group in the Janssen (Johnson & Johnson) COVID-19 vaccine clinical trial, compared to one Guillain-Barré syndrome case among those who received placebo. With few exceptions, ACIP’s general best practice guidelines for immunization do not include history of Guillain-Barré syndrome as a contraindication or precaution to vaccination. People with a history of Guillain-Barré syndrome may receive COVID-19 vaccination. Any occurrence of Guillain-Barré syndrome following COVID-19 vaccination should be reported to VAERS.

People with a history of Bell’s palsy

Cases of Bell’s palsy were reported following vaccination of participants in the COVID-19 vaccine clinical trials. However, the FDA does not consider these to be above the frequency expected in the general population and has not concluded that these cases were causally related to vaccination. Post-authorization safety surveillance will be important to further assess any possible causal association. In the absence of such evidence, people with a history of Bell’s palsy can receive a COVID-19 vaccine. Any occurrence of Bell’s palsy following COVID-19 vaccination should be reported to the Vaccine Adverse Event Reporting System (VAERS).

People with a history of dermal filler use

Infrequently, people who have received dermal fillers might experience swelling at or near the site of filler injection (usually face or lips) following administration of a dose of an mRNA COVID-19 vaccine (no similar occurrences were observed in the Janssen [Johnson & Johnson] COVID-19 vaccine clinical trials). The swelling appears to be temporary and resolves with medical treatment, including corticosteroid therapy. COVID-19 vaccines can be administered to people who have received injectable dermal fillers who have no contraindications or precautions for vaccination. However, these people should be advised to contact their healthcare provider for evaluation if they experience swelling at or near a dermal filler site following vaccination.

Pregnancy and COVID-19

Observational data demonstrate that pregnant people with COVID-19 have an increased risk of severe illness, including illness resulting in intensive care admission, mechanical ventilation, extracorporeal membrane oxygenation, or death, though the absolute risk for these outcomes is low. Additionally, they might be at an increased risk of adverse pregnancy outcomes, such as preeclampsia, coagulopathy, and preterm birth.

It may be possible for you to pass COVID-19 to your baby before they are born. But when this has happened, the babies have got better.

Data on the safety of COVID-19 vaccines in pregnant people are limited. No female reproduction or fetal, embryonal, or postnatal development safety concerns were demonstrated in animals that received Pfizer-BioNTech, Moderna, or Janssen [Johnson & Johnson] COVID-19 vaccines before or during gestation. In addition, the adenovirus vector platform used in the Janssen (Johnson & Johnson) COVID-19 vaccine has also been used for other Janssen vaccine development programs that have included pregnant people vaccinated during any trimester, including in a large-scale Ebola vaccination trial. No adverse pregnancy-related outcomes—including infant outcomes—were determined to be related to the vaccine in these trials.

Based on current knowledge, experts believe that COVID-19 vaccines are unlikely to pose a risk to the pregnant person or fetus because the currently authorized COVID-19 vaccines are non-replicating vaccines and cannot cause infection in either the mother or the fetus. No evidence exists of risk to the fetus from vaccinating pregnant women with non-replicating vaccines in general. However, the potential risks of COVID-19 vaccines to the pregnant person and the fetus are unknown because these vaccines have not been studied in pregnant people. Clinical trials to evaluate the safety and efficacy of COVID-19 vaccines in pregnant people are underway or planned. Vaccine manufacturers are also following outcomes in people in the clinical trials who became pregnant.

Pregnant people may choose to receive a COVID-19 vaccine. A conversation between the patient and their clinical team may assist with decisions about the use of a COVID-19 vaccine, though a conversation with a healthcare provider is not required before vaccination. When making a decision, pregnant people and their healthcare providers should consider the level of COVID-19 community transmission, the patient’s personal risk of contracting COVID-19, the risks of COVID-19 to the patient and potential risks to the fetus, the efficacy of the vaccine, the side effects of the vaccine, and the limited data about the vaccine during pregnancy. Pregnant people who choose to receive COVID-19 vaccine are encouraged to enroll in v-safe. V-safe is a smartphone-based tool that uses text messaging and web surveys to provide personalized health check-ins after you receive a COVID-19 vaccine. Through v-safe, you can quickly tell CDC if you have any side effects after getting the COVID-19 vaccine. Depending on your answers, someone from CDC may call to check on you and get more information. V-safe will also remind you to get your second COVID-19 vaccine dose if you need one. A v-safe pregnancy registry has been established to follow outcomes among pregnant people who are vaccinated. Based on self-reported information, no specific safety signals have been observed among pregnant vaccine recipients included in the v-safe registry. However longitudinal follow-up is needed to fully evaluate pregnancy and birth outcomes.

Side effects can occur with COVID-19 vaccine use in pregnant people, similar to those expected among non-pregnant people. Acetaminophen can be offered as an option for pregnant people experiencing fever (which has been associated with adverse pregnancy outcomes) or other post-vaccination symptoms.

There is no recommendation for routine pregnancy testing before receipt of a COVID-19 vaccine. Those who are trying to become pregnant do not need to avoid pregnancy after COVID-19 vaccination. There is no evidence that any of the COVID-19 vaccines affect future fertility.

COVID-19 vaccines in breastfeeding

There are no data on the safety of COVID-19 vaccines in lactating people or the effects of COVID-19 vaccines on the breastfed infant or milk production or excretion. Because non-live vaccines pose no risk for lactating people or their infants, COVID-19 vaccines are also not thought to be a risk. Therefore, lactating people may choose to be vaccinated.

COVID-19 vaccine advice if you’re of childbearing age, pregnant or breastfeeding

You should wait to have the COVID-19 vaccine:

• if you’re pregnant you should not be vaccinated – you should wait until you’ve had your baby
• if you’re breastfeeding – you should wait until you’ve stopped breastfeeding
• If you were breastfeeding when you had the first dose you are advised not to have the second dose until you have finished breastfeeding
• if you are planning to get pregnant in the next 3 months, you should delay your vaccination
• if you know you are not pregnant you can start the two-dose course now and you should avoid getting pregnant until at least 2 months after the second dose
• if you have had the first dose and then become pregnant you should delay the second dose until after the pregnancy is over

If you have the COVID-19 vaccine, you should not get pregnant for at least 2 months after having the 2nd dose.

If you later find out you were pregnant when you had the COVID-19 vaccine, do not worry. The vaccine cannot give you or your baby COVID-19.

There’s no evidence it’s unsafe if you’re pregnant or breastfeeding. But more evidence is needed before you can be offered the vaccine.

This advice is precautionary until additional evidence is available to support the use of this vaccine in pregnancy and breastfeeding.

What to do if you’re pregnant

If you’re pregnant, it’s important you:

• wash your hands regularly
• stay at home as much as possible and follow the advice on social distancing, such as staying at least 2 meters (3 steps) away from other people
• stay away from anyone who has symptoms of COVID-19

You still need to go to all of your pregnancy (antenatal) scans and appointments unless you’re told not to.

You may find that:

• some midwife appointments are online, by phone or by video call
• you may be asked to wear a mask or gown when you’re in a hospital or clinic
• some appointments may be cancelled or rescheduled – if an appointment is cancelled, it will be rescheduled, or you’ll be able to rebook it

This is to help keep everyone safe and stop the spread of COVID-19.

If you’re unsure if you can bring your partner to your appointment, ask your midwife or maternity team.

What are the risks of the Pfizer-BioNTech COVID-19 vaccine?

Side effects that have been reported with the Pfizer-BioNTech COVID-19 vaccine include ²⁰:

• injection site pain
• tiredness
• headache
• muscle pain
• chills
• joint pain
• fever
• injection site swelling
• injection site redness
• nausea
• feeling unwell
• swollen lymph nodes (lymphadenopathy)

There is a remote chance that the Pfizer-BioNTech COVID-19 vaccine could cause a severe allergic reaction. A severe allergic reaction would usually occur within a few minutes to one hour after getting a dose of the Pfizer-BioNTech COVID-19 Vaccine. Signs of a severe allergic reaction can include ²⁰:

• Difficulty breathing
• Swelling of your face and throat
• A fast heartbeat
• A bad rash all over your body
• Dizziness and weakness

If you experience a severe allergic reaction, call your local emergency services number or go to the nearest hospital.

These may not be all the possible side effects of the Pfizer-BioNTech COVID-19 Vaccine. Serious and unexpected side effects may occur. Pfizer-BioNTech COVID-19 Vaccine is still being studied in clinical trials.

COVID-19 vaccines contraindications

The CDC considers a history of the following to be a contraindication to vaccination with COVID-19 vaccines:

• Severe allergic reaction (e.g., anaphylaxis) after a previous dose or to a component of the COVID-19 vaccine
• Immediate allergic reaction of any severity to a previous dose or known (diagnosed) allergy to a component of the vaccine

Polyethylene glycol (PEG) is an ingredient in both mRNA COVID-19 vaccines, and polysorbate 80 is an ingredient in Janssen (Johnson & Johnson) COVID-19 vaccine. PEG and polysorbate are structurally related, and cross-reactive hypersensitivity between these compounds may occur. Known polysorbate allergy is not a contraindication to mRNA vaccination; however, known polysorbate allergy is a contraindication to Janssen (Johnson & Johnson) COVID-19 vaccine and thus, a precaution to mRNA COVID-19 vaccination. People with a contraindication to one of the mRNA COVID-19 vaccines should not receive doses of either of the mRNA vaccines (Pfizer-BioNTech or Moderna). However, people with a contraindication to mRNA COVID-19 vaccines may be able to receive Janssen (Johnson & Johnson) COVID-19 vaccine, and vice versa, provided certain measures are taken.

COVID-19 vaccine side effects

Local reactions at the injection site were found to be fairly common after vaccination with the Pfizer-BioNTech COVID-19 vaccine (BNT162b2) during clinical trials. Over 80% of trial participants reported pain at the injection site. This occurred within 7 days after the injection and resolved after a few days. In clinical trials, the most frequently reported systemic reactions in participants were tiredness (reported by more than 60% of participants), headache (> 50%), muscle aches (> 30%), chills (> 30%), joint pain (> 20%) and a raised temperature (pyrexia) (> 10%). These symptoms were usually mild or moderate in intensity and resolved within a few days after vaccination. Of note, more people experienced these side effects after the second dose than after the first dose, so it is important for vaccination providers and recipients to expect that there may be some side effects after either dose, but even more so after the second dose. If required, symptomatic treatment with analgesic and/or anti-pyretic medicinal products (e.g., acetaminophen [paracetamol] containing products) may be used.

The most frequently reported adverse reactions to the Moderna COVID-19 vaccine were injection site pain (92%), fatigue (70%), headache (65%), muscle aches (myalgia) (62%), joint pain (arthralgia) (46%), chills (46%), nausea/vomiting (23%), armpit swelling/tenderness (19.8%), fever (15.5%), injection site swelling (14.7%) and redness (10%). Adverse reactions were usually mild or moderate in intensity and resolved within a few days after vaccination. Older vaccinees experienced a slightly lower frequency of reactions. Overall, there was a higher incidence of some adverse reactions in younger age groups: the incidence of armpit swelling/tenderness, fatigue, headache, myalgia, arthralgia, chills, nausea or vomiting and fever was higher in adults aged 18 to < 65 years than in those aged 65 years and above. Local and systemic adverse reactions were more frequently reported after the second dose than after the first dose. If required, symptomatic treatment with analgesic and/or anti-pyretic medicinal products (for example, acetaminophen [paracetamol] -containing products) may be used.

More than 60% of AstraZeneca COVID-19 vaccine trial participants reported tenderness at the injection site with redness, swelling, itching, warmth and pain at the injection site also being reported. The most frequently reported systemic reactions were headache and tiredness (by more than 50% of participants); muscle aches and feeling generally unwell (>40%); raised temperature (pyrexia) and chills (>30%) and joint pain and nausea (>20%). The majority of adverse events reported during the clinical trials of the AstraZeneca COVID-19 vaccine were mild to moderate and short-lasting, usually resolving within a few days of vaccination. When compared with the first dose, adverse reactions reported after the second dose were milder and reported less frequently. Prophylactic use of acetaminophen [paracetamol] was found not to affect the immune response to this vaccine.

Call the vaccination provider or your healthcare provider if you have any side effects that bother you or do not go away.

Report vaccine side effects to the FDA or the CDC Vaccine Adverse Event Reporting System (VAERS). The VAERS toll-free number is 1-800-822-7967 or report online to https://vaers.hhs.gov/reportevent.html. Please include “Pfizer-BioNTech COVID-19 Vaccine EUA” in the first line of box #18 of the report form.

Allergic reactions (including severe allergic reactions) not related to vaccines (COVID-19 or other vaccines) or injectable therapies, such as allergic reactions related to food, pet, venom, or environmental allergies, or allergies to oral medications (including the oral equivalents of injectable medications), are not a contraindication or precaution to COVID-19 vaccination. The vial stoppers of COVID-19 vaccines are not made with natural rubber latex, and there is no contraindication or precaution to vaccination for people with a latex allergy. In addition, because the COVID-19 vaccines do not contain eggs or gelatin, people with allergies to these substances do not have a contraindication or precaution to vaccination.

Delayed-onset local reactions have been reported after mRNA vaccination in some individuals beginning a few days through the second week after the first dose and are sometimes quite large. People with only a delayed-onset local reaction (e.g., redness, swelling, itch) around the injection site area after the first vaccine dose do not have a contraindication or precaution to the second dose. These individuals should receive the second dose using the same vaccine product as the first dose at the recommended interval, preferably in the opposite arm.

References

1. COVID-19 Vaccines. https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/covid-19-vaccines
2. https://www.modernatx.com/covid19vaccine-eua/eua-fact-sheet-recipients.pdf
3. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/961037/NERVTAG_note_on_B.1.1.7_severity_for_SAGE_77__1_.pdf
4. mRNA-1273 vaccine induces neutralizing antibodies against spike mutants from global SARS-CoV-2 variants. Kai Wu, Anne P. Werner, Juan I. Moliva, Matthew Koch, Angela Choi, Guillaume B. E. Stewart-Jones, Hamilton Bennett, Seyhan Boyoglu-Barnum, Wei Shi, Barney S. Graham, Andrea Carfi, Kizzmekia S. Corbett, Robert A. Seder, Darin K. Edwards bioRxiv 2021.01.25.427948; doi: https://doi.org/10.1101/2021.01.25.427948
5. Comprehensive mapping of mutations to the SARS-CoV-2 receptor-binding domain that affect recognition by polyclonal human serum antibodies. Allison J. Greaney, Andrea N. Loes, Katharine H.D. Crawford, Tyler N. Starr, Keara D. Malone, Helen Y. Chu, Jesse D. Bloom bioRxiv 2020.12.31.425021; doi: https://doi.org/10.1101/2020.12.31.425021
6. Escape from neutralizing antibodies by SARS-CoV-2 spike protein variants. eLife 2020;9:e61312 doi: 10.7554/eLife.61312
7. Spike E484K mutation in the first SARS-CoV-2 reinfection case confirmed in Brazil, 2020. https://virological.org/t/spike-e484k-mutation-in-the-first-sars-cov-2-reinfection-case-confirmed-in-brazil-2020/584
8. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/963838/AZD1222_Information_for_Healthcare_Professionals_-_22-02-2021.pdf
9. Safety of COVID-19 Vaccines. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html
10. Selected Adverse Events Reported after COVID-19 Vaccination. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html
11. What to Do If You Have an Allergic Reaction after Getting a COVID-19 Vaccine. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/allergic-reaction.html
12. The Possibility of COVID-19 after Vaccination: Breakthrough Infections. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness/why-measure-effectiveness/breakthrough-cases.html
13. EMERGENCY USE AUTHORIZATION (EUA) OFTHE PFIZER-BIONTECH CO VID-19 VACCINE TO PREVENT CORONAVIRUS DISEASE 2019 (CO VID-19) IN INDIVIDUALS 16 YEARS OF AGE AND OLDER. https://www.fda.gov/media/144414/download
14. 4-hydroxybutyl)azanediyl) bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2 [(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3-phosphocholine, and cholesterol), potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose.

    Table 4. Ingredients included in COVID-19 vaccines

    Description	Pfizer-BioNTech (mRNA)	Moderna (mRNA)	Janssen [Johnson & Johnson] (viral vector)
    Active ingredient	Nucleoside-modified mRNA encoding the viral spike (S) glycoprotein of SARS-CoV-2	Nucleoside-modified mRNA encoding the viral spike (S) glycoprotein of SARS-CoV-2	Recombinant, replication-incompetent Ad26 vector, encoding a stabilized variant of the SARS-CoV-2 Spike (S) protein
    Inactive ingredients	2[(polyethylene glycol (PEG 2-hydroxyethyl) (6-oxo-6-(undecyloxy) hexyl) amino) octanoate	Trisodium citrate dihydrate
    	Sodium chloride	Tromethamine	Sodium chloride
    	Monobasic potassium phosphate	Tromethamine hydrochloride	Sodium hydroxide
    	Potassium chloride	Acetic acid	Hydrochloric acid
    	Dibasic sodium phosphate dihydrate	Sodium acetate	Ethanol
    	Sucrose	Sucrose	Water for injection

    Footnotes: * None of the vaccines contain eggs, gelatin, latex, or preservatives. Both the Pfizer-BioNTech and Moderna COVID-19 vaccines contain polyethylene glycol (PEG). PEG is a primary ingredient in osmotic laxatives and oral bowel preparations for colonoscopy procedures, an inactive ingredient or excipient in many medications, and is used in a process called “pegylation” to improve the therapeutic activity of some medications (including certain chemotherapeutics). Additionally, cross-reactive hypersensitivity between PEG and polysorbates (included as an excipient in some vaccines and other therapeutic agents) can occur. Information on active or inactive ingredients for vaccines and medications can be found in the package insert. CDC’s vaccine excipient summary (https://www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/b/excipient-table-2.pdf) and the National Institutes of Health DailyMed database (https://dailymed.nlm.nih.gov/dailymed/index.cfm) can also be used as a resource.

    How effective is the Pfizer BioNTech COVID-19 vaccine?

    The effectiveness data to support the Pfizer BioNTech COVID-19 Vaccine EUA include an analysis of 36,523 participants in the ongoing randomized, placebo-controlled international study, the majority of whom are U.S. participants, who did not have evidence of SARS-CoV-2 infection through seven days after the second dose. Among these participants, 18,198 received the vaccine and 18,325 received placebo. The vaccine was 95% effective in preventing COVID-19 disease among these clinical trial participants with eight COVID-19 cases in the vaccine group and 162 in the placebo group. Of these 170 COVID-19 cases, one in the vaccine group and three in the placebo group were classified as severe. At this time, data are not available to make a determination about how long the vaccine will provide protection, nor is there evidence that the vaccine prevents transmission of SARS-CoV-2 from person to person ((FDA Takes Key Action in Fight Against COVID-19 By Issuing Emergency Use Authorization for First COVID-19 Vaccine. https://www.fda.gov/news-events/press-announcements/fda-takes-key-action-fight-against-covid-19-issuing-emergency-use-authorization-first-covid-19

15. Clift AK, Coupland CAC, Keogh RH et al. Living risk prediction algorithm (QCOVID) for risk of hospital admission and mortality from coronavirus 19 in adults: national derivation and validation cohort study. BMJ. 2020 Oct 20;371:m3731
16. Modelling optimal vaccination strategy for SARS-CoV-2 in the UK. Sam Moore, Edward M Hill, Louise Dyson, Michael Tildesley, Matt J Keeling. medRxiv 2020.09.22.20194183; doi: https://doi.org/10.1101/2020.09.22.20194183
17. Ladhani SN, Chow JY, Janarthanan R et al. London Care Home Investigation Team. Increased risk of SARS-CoV-2 infection in staff working across different care homes: enhanced CoVID-19 outbreak investigations in London care Homes. J Infect. 2020 Jul 29;81(4):621-4.
18. Ladhani SN, Chow JY, Janarthanan R et al. Investigation of SARS-CoV-2 outbreaks in six care homes in London, April 2020. EClinicalMedicine. 2020 Sep 9:100533
19. EMERGENCY USE AUTHORIZATION (EUA) OF THE PFIZER-BIONTECH COVID-19 VACCINE TO PREVENT CORONAVIRUS DISEASE 2019 (CO VID-19) IN INDIVIDUALS 16 YEARS OF AGE AND OLDER. https://www.fda.gov/media/144414/download