About the COVID-19 Vaccine: Frequently Asked Questions

Q: Which COVID-19 vaccine should I recommend to my patients?

A: COVID-19 vaccines are life-saving vaccines. Delaying immunization leaves an individual vulnerable to infection for a longer period of time, placing them at greater risk of serious illness and death. AAP recommends COVID-19 vaccination for all children and adolescents 5 years of age and older who do not have contraindications using a COVID-19 vaccine approved through an Emergency Use Authorization (EUA) or Biologics License Application (BLA), recommended by CDC, and appropriate for their age and health status. AAP also supports coadministration of COVID-19 vaccines with other vaccines on the immunization schedule. See AAP policy.

Research trials have shown COVID-19 vaccines are highly effective against severe COVID-19 illness, hospitalization, and death. Those who are 5-17 years old should receive the Pfizer-BioNTech vaccine; while those 18 years of age or older may receive what is recommended and available in their community, with a preference for mRNA vaccine (ie. Pfizer-BioNTech or Moderna).

Q: What do we know about the new SARS-CoV-2 variants and vaccine efficacy?

A: Multiple variants of SARS-CoV-2 have been documented in the United States and globally during this pandemic. Data show that vaccines may be less effective against Omicron variant in preventing infection and that effectiveness may diminish over time; however, they are still effective in preventing hospitalization and death. The AAP continues to support COVID vaccination among the population as it is the best way to prevent severe morbidity and mortality from SARS-CoV-2. A report published in the New England Journal of Medicine in March 2022 provides updated information about vaccine effectiveness in children and adolescents during the Delta-predominant and Omicron-predominant periods. Expert analysis of this article can be found in the March 31 AAP COVID-19 Town Hall recording at 10:44.

During Omicron variant predominance beginning in late December 2021, U.S. infants and children aged 0–4 years were hospitalized at approximately five times the rate of the previous peak during Delta variant predominance. Further, COVID-19–associated hospitalization rates in children aged 5–11 years were approximately twice as high among unvaccinated as among vaccinated children. Thus, important strategies should be utilized to prevent COVID-19 among infants and children, including vaccination of currently eligible populations such as children 5 years of age and older, pregnant women, family members, and caregivers of infants and young children.

New COVID-19 Variants | CDC

Q: Which COVID-19 vaccines have been approved and/or authorized for use in the US? 

A: The US has two mRNA and one viral vector COVID-19 vaccines for use in response to the pandemic. The CDC has recommended COVID-19 vaccines with a preference for people to receive an mRNA vaccine (Pfizer-BioNTech and Moderna). Janssen vaccine is available for individuals who are unable or unwilling to receive an mRNA vaccine. 

Pfizer-BioNTech mRNA Vaccine

• FDA BLA approval for individuals 16 years of age and older / CDC ACIP Recommendation
• FDA EUA for adolescents 12 – 15 years of age / CDC ACIP Recommendation
• FDA EUA for children 5-11 years of age / CDC ACIP Recommendation
• FDA EUA for a dose in severely immunocompromised individuals 5 years of age and older / CDC ACIP Recommendation
• FDA EUA for a booster dose at least 5 months following primary series for all individuals 12 years of age and older / CDC ACIP Recommendation
• FDA EUA for a booster dose at least 5 months following primary series for all individuals 5-11 years of age / CDC ACIP Recommendation

Moderna mRNA Vaccine

• FDA BLA approval for individuals 18 years of age and older / CDC ACIP Recommendation
• FDA EUA for 3-dose primary series in severely immunocompromised individuals 18 years of age and older / CDC ACIP Recommendation
• FDA EUA for a booster dose at least 5 months following primary series for all individuals 18 years of age and older / CDC ACIP Recommendation

Janssen (J&J) Viral Vector Vaccine

• FDA EUA for individuals 18 years of age and older / FDA EUA Amendment / CDC ACIP Recommendation
• FDA EUA for a booster dose at least 2 months after a 1-dose of Janssen (J&J) / CDC ACIP Recommendation

As we near the anticipated approval of vaccine for children ages 6 months to 4 years, consider reviewing the CDC Pediatric COVID-19 Operational Planning Guide which can be accessed here.

Q: Which Pfizer-BioNTech vaccine dose should a child receive if they are 11 years of age, but will turn 12 years old before they can receive a second dose?

A: The CDC recommends providing children with the dose that is recommended for their age at the time of vaccine administration. For example, an 11 year old child should receive 10 mcg - the pediatric formulation for children ages 5-11 (orange cap). If this child turns 12 prior to returning for their second dose 21 days later, they should receive 30 mcg - the original formulation (grey or purple cap) for adolescents age 12 and older.

If a child turns from 11 to 12 years of age in between their first and second dose and receives the pediatric formulation for their second dose, they do not need to repeat the dose.

Q: What are the vaccine recommendations for children and adolescents who are moderately to severely immunocompromised?

A: Pediatricians who care for children and adolescents with certain immunocompromising medical conditions or who are receiving treatments that induce moderate to severe immune suppression should encourage their patients to be vaccinated with a 3-dose primary series of mRNA vaccine; the Pfizer-BioNTech vaccine for 5-17 year olds and either the Pfizer-BioNTech vaccine or Moderna vaccine for those 18 years of age and older (see CDC Clinical Considerations for a list of conditions). The recommended interval between dose 1 and dose 2 is 21 days for Pfizer-BioNTech and 28 days for Moderna. The recommended interval between dose 2 and dose 3 is at least 4 weeks after the 2nd dose for either vaccine product. It is recommended that the same mRNA vaccine product be used for all doses in the primary series.

Patients who are 5 years of age and older should also receive a booster dose 3 months after their 3rd dose. While any product may be used for those 18 years of age and older, there is a preference for mRNA vaccine. Patients 12 years of age and older are also allowed to receive a second booster dose (must be an mRNA vaccine) 4 months after their first booster dose. Prior to and following COVID-19 vaccine administration, infection prevention measures should continue such as wearing a mask, physical distancing, and avoiding crowds and poorly ventilated indoor spaces, as immunocompromised individuals may still be at increased risk for COVID-19. Close contacts of immunocompromised individuals who are eligible should receive COVID-19 vaccination to provide additional protection.

Information on immunization and immunocompromised children and adolescents can be found in the:

Red Book: Immunization and Other Considerations in Immunocompromised Children | Red Book® 2021 | Red Book Online | AAP Point-of-Care-Solutions

CDC Clinical Considerations: https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html 

Talking with Patients Who Are Immunocompromised: https://www.cdc.gov/vaccines/covid-19/clinical-considerations/immunocompromised-patients.html

Q: Should patients receive a booster dose of COVID-19 vaccine?

A: Yes. The protection COVID-19 vaccines provide decreases over time, especially for certain groups of people. CDC recommends the use of a single booster dose for all individuals 5 years of age and older. Those who received the Pfizer-BioNTech COVID-19 or Moderna vaccine as their primary series should receive a booster dose at least five months after completion of their 2-dose primary series. Those who received the Janssen (J&J) COVID-19 vaccine should receive a booster dose 2 months following their initial dose. Any EUA authorized and approved COVID vaccine can be used for the single dose booster for individuals 18 years of age and older, however, there is preference for people to receive an mRNA vaccine (ie Pfizer-BioNTech 30 mcg or Moderna 50 mcg). Janssen (J&J) 0.5 ml can be used for individuals who are unable or unwilling to receive an mRNA vaccine booster.

Individuals who are 12-17 years of age should receive a single booster dose of Pfizer-BioNTech COVID-19 Vaccine (COMIRNATY) 30 mcg at least 5 months after the final dose in the primary series.

Individuals who are 5-11 years of age should receive a single booster dose of Pfizer-BioNTech COVID-19 Vaccine 10 mcg at least 5 months after the final dose in the primary series.
The CDC offers more information about booster doses, including eligibility and answers to frequently asked questions.

Experts continue to recommend that everyone get vaccinated and boosted, regardless of whether they’ve had COVID-19 in the past. As cases increase across the country, a booster dose will safely help restore and enhance protection against severe disease.

Q: Can I administer a COVID-19 vaccine to a patient who is currently sick with COVID-19?

A: COVID-19 vaccination should be deferred for patients with a current SARS-CoV-2 infection until they recover from their acute illness and the criteria to discontinue isolation has been met. Patients who are asymptomatic should receive COVID-19 vaccine following their recommended isolation period. This also applies to people who become infected with COVID-19 between their first and second dose of vaccine, or those who are due for a booster.

Individuals who recently had SARS-CoV-2 infection and have concluded their isolation period may consider delaying a primary series dose or their first or second COVID-19 vaccine booster dose by 3 months from symptom onset or positive test (if infection was asymptomatic). Studies have shown that increased time between infection and vaccination may result in an improved immune response to vaccination.

Q: What is the difference between COVID-19 mRNA and viral vector vaccines?

A: Messenger RNA (mRNA) Vaccines
These vaccines use a newer technology where mRNA is wrapped in a coating (lipid nanoparticle) so it can enter our cells. The mRNA in the vaccine teaches our cells how to make copies of a spike protein. Once the spike protein is made, two things occur: (1) the cell breaks down the mRNA (instructions) and gets rid of them, and (2) the spike protein triggers an immune response inside of our bodies, which produces antibodies. These antibodies protect us from getting infected if the real virus enters our bodies.

Viral Vector Vaccines
Viral vector vaccines use a modified, harmless version of a different virus to deliver instructions to our cells. The virus enters the cell and teaches it how to make copies of a spike protein, which then triggers an immune response inside of our bodies. This immune response results in the production of antibodies which protect us from getting infected if the real virus enters our bodies.

Q: What is the current status of COVID-19 vaccine research in children and adolescents? 

A: 

• Pfizer-BioNTech is in the process of testing its COVID-19 vaccine in children younger than 5 years down to age six months. It is anticipated that data will be submitted for FDA consideration in May 2022.
• Moderna submitted data to the FDA on a 50 mcg dose for the adolescent series (12-17 years of age), a 25 mcg dose for the pediatric series (6-11 years of age), and a 25 mcg dose for their series in children 6 months through 5 years of age.
• Novavax completed enrollment of its pediatric clinical trial looking at their recombinant protein vaccine candidate against COVID-19 in adolescents 12 to 17 years old. This study will include 3,000 adolescents aged 12-17 across up to 75 sites in the United States.
• Janssen and Astra Zeneca also have plans to study their vaccines in younger age groups.

The AAP actively advocated for the inclusion of children and pregnant women in COVID-19 vaccine trials, and sent multiple letters and comments to FDA, the Vaccines and Related Biological Products Advisory Committee (VRBPAC), the White House COVID-19 Response Team; and has also issued multiple press statements.

Q: When will COVID-19 vaccines be available to pediatric populations? 

A: Currently, the Pfizer-BioNTech COVID-19 vaccine is authorized for emergency use in children and adolescents 5 years of age and older. Additional trials are being conducted in younger populations, as well as with other COVID-19 vaccine products. Reports from Pfizer-BioNTech indicate that the vaccine is safe and highly effective among the adolescent population (12-17 year olds) as well as for 5-11 year olds.

Q: Is it safe for pregnant or lactating women to receive COVID-19 vaccine? 

A: Safety data have showed no major concerns reported in pregnant persons. Additionally, recent studies show that vaccination during pregnancy with a 2-dose mRNA COVID-19 vaccine series may help prevent COVID-19 hospitalizations in infants < 6 months of age. The CDC has issued a Health Alert Network Advisory strongly recommending urgent action to increase COVID-19 vaccination before or during pregnancy as the benefits outweigh known or potential risks.

Guidance is also available from the American College of Obstetricians and Gynecologists (ACOG).

Q: Does COVID-19 vaccine affect fertility or puberty?  

A: Unfounded claims linking COVID-19 vaccines to infertility have been scientifically disproven. There is no evidence that the vaccine can lead to loss of fertility. While fertility was not specifically studied in the clinical trials of the vaccine, no loss of fertility has been reported among trial participants or among the millions who have received the vaccines since their authorization, and no signs of infertility appeared in animal studies. Similarly, there is no evidence that the COVID-19 vaccine affects puberty. 

Q: When is a vaccine recipient considered fully vaccinated, and how long does immunity last?

A: An individual is considered fully vaccinated two weeks after completion of a COVID-19 vaccine primary series. Fully vaccinated, however, is not the same as having the best protection which comes from being up to date on all recommended doses, including boosters. Data show that vaccines may be less effective against Omicron variant in preventing infection and that effectiveness may diminish over time; however, are still effective in preventing COVID-19 hospitalization and death. As a result of decreasing efficacy, the FDA and CDC recommend use of a single booster dose for all individuals 5 years of age and older.

Q: Are there any safety concerns with the new technologies (mRNA and nanotechnology) being used in the development of the Pfizer-BioNTech and Moderna COVID-19 vaccines?

A: There are no known additional risks of mRNA vaccines or lipid nanoparticles. Live attenuated viral vaccines, such as measles vaccine, induce an immune response that is similar to natural infection. mRNA vaccines, on the other hand, simply give the body instructions to produce one very specific part of a virus – in this case the so-called spike protein – to then induce an immune response. Because mRNA is broken down very quickly in the human body, to do its work it needs to be able to get into our cells, and so it is wrapped in a lipid nanoparticle. Once it gets into the cells to deliver the instructions, the mRNA breaks down very quickly. It does not get into the nucleus of the cell, or into our genes. Since the new mRNA vaccines have been administered, their safety profiles are reassuring.

Since April 2021, rare cases of myocarditis and pericarditis have been reported in adolescents and young adults (under 30 years of age) following receipt of mRNA vaccines – most often following the 2^nd dose. However, studies show that risk of myocarditis in this population was up to 6 times higher post SARS-CoV-2 infection than post mRNA vaccines. Post vaccine myocarditis is milder, requiring shorter hospital stays (1-2 days) vs. myocarditis caused by SARS-CoV-2 infection which has been more severe requiring a hospital stay of 5 days on average. Pediatricians should consider myocarditis and pericarditis in adolescents or young adults with acute chest pain, shortness of breath, or palpitations and report any suspected cases post COVID-19 vaccination to VAERS. History of myocarditis of pericarditis after a dose of an mRNA vaccine is also listed as a precaution for future doses. CDC continues to monitor the situation and has created guidance for health care providers.

Clinical Considerations: Myocarditis after mRNA COVID-19 Vaccines | CDC 

Q: What side effects are noted to date with COVID-19 mRNA vaccines (Pfizer-BioNTech and Moderna)?

A: The side effects have been similar to other routine vaccines- sore arm, redness, fatigue, fever, chills, headache, myalgia, and arthralgia. The side effects are temporary and mostly mild or moderate. Side effects may be worse after the second dose in some individuals. Anaphylaxis has been observed following receipt of COVID-19 mRNA vaccines, but this has been rare. Extremely rare cases of myocarditis or pericarditis have been reported – most often in males between 12-39 years of age – and most often following the 2nd dose. A full listing of the side effects is now available on the FDA website and a summary is found in the fact sheet that is provided to everyone who receives the vaccine. The potential for side effects that cause individuals to miss work should also be considered in planning.

Allergic Reactions Including Anaphylaxis After Receipt of the First Dose of Pfizer-BioNTech COVID-19 Vaccine — United States, December 14–23, 2020 | MMWR (cdc.gov)

Allergic Reactions Including Anaphylaxis After Receipt of the First Dose of Moderna COVID-19 Vaccine — United States, December 21, 2020–January 10, 2021 | MMWR (cdc.gov)

Q: What side effects are noted to date with the Janssen COVID-19 viral vector vaccine? Are there any contraindications? 

A: Common side effects post vaccination are pain, redness, and swelling in the arm where you received the shot, as well as, tiredness, headache, muscle pain, chills, fever, and nausea within the first few days.

CDC considers the following to be a contraindication to receiving Janssen COVID-19: Severe allergic reaction or immediate allergic reaction of any severity to a previous dose or component of Janssen COVID-19 vaccine. Precautions should be taken for individuals with a history of immediate allergic reaction to another vaccine or injectable therapy and those with moderate or severe acute illness.

Additionally, in December 2021, the FDA revised the EUA Fact Sheet for Janssen COVID-19 vaccine to include: (1) a contraindication for individuals with a history of thrombosis with thrombocytopenia following the Janssen COVID-19 vaccine or any other adenovirus-vectored COVID-19 vaccines; and (2) a warning and precaution for Thrombosis with Thrombocytopenia Syndrome (TTS) as cases of TTS following administration have been reported in males and females 18 years of age and older, with the highest rate in females aged 30-49 years. Providers should maintain a high level of suspicion for symptoms that might represent serious thrombotic events or thrombocytopenia in patients who have recently received the Janssen COVID-19 vaccine. See CDC Health Alert Network for additional information: https://emergency.cdc.gov/han/2021/han00442.asp

On July 12, the FDA announced it is adding a warning label to the Janssen COVID-19 vaccine, due to an increased risk of a rare neurological syndrome called Guillain-Barré syndrome (GBS). The new warning label is based on preliminary data, after about 100 reports of GBS were detected in the Vaccine Adverse Event Reporting System, out of more than 12.8 million administered doses of the Janssen vaccine administered. Each year an estimated 3,000 to 6,000 people develop GBS in the US from various causes. Most people fully recover from the disorder.

The CDC has recommended COVID-19 vaccines with a preference for people to receive an mRNA vaccine (Pfizer-BioNTech and Moderna). Janssen vaccine is available for individuals who are unable to unwilling to receive an mRNA vaccine. 

Q: Are there any contraindications to receiving COVID-19 mRNA vaccines from Pfizer-BioNTech and Moderna?

A: CDC considers the following to be a contraindication to vaccination with both Pfizer-BioNTech and Moderna COVID-19 vaccines: Severe allergic reaction (eg., anaphylaxis) after a previous dose of an mRNA COVID-19 vaccine or any of its components, immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components (including polyethylene glycol [PEG]), and immediate allergic reaction of any severity to polysorbate (due to potential cross-reactive hypersensitivity with the vaccine ingredient PEG)*

In persons who report a history of anaphylaxis to another vaccine (i.e., any other vaccine besides the Pfizer-BioNTech and Moderna COVID-19 vaccine) or injectable therapy, a risk assessment should be conducted to determine type of reaction and certainty of information. A small number of vaccine recipients have experienced anaphylaxis following receipt of the Pfizer vaccine, so all patients should be monitored for at least 15 minutes following COVID-19 vaccine administration. Patients with a history of severe allergic reaction (due to any cause) should be monitored for at least 30 minutes following administration. Patients who experience anaphylaxis following the first dose of COVID-19 vaccine should be counseled not to receive the second dose and referred to an allergist-immunologist for appropriate follow up.

Q: Do we need to worry about an increase in MIS-C in kids receiving COVID-19 vaccine?

A: To date, MIS-C has not occurred following receipt of COVID-19 vaccine without SARS-CoV-2 infection. In fact, COVID-19 vaccine offers protection against MIS-C, as a recent study demonstrated that receipt of 2 doses of Pfizer-BioNTech COVID-19 vaccine is highly effective in preventing MIS-C in persons 12-18 years of age.

Q: What is the safety testing that has been done on COVID-19 vaccines? How do we know it is safe long-term?

A: The safety follow-up for COVID-19 vaccines is essentially the same that it is for all vaccine trials. The expectation for the adult phase 3 trials is 2 years of safety follow-up - longer than for most vaccines during development. It is impossible to know the very long-term safety profile of vaccines that have only been in humans for about  18 months. That said, no vaccines licensed have been found to have an unexpected long-term safety problem, that was found only years or decades after introduction.

Q: What vaccine safety surveillance programs are in place?

A: All COVID-19 vaccines approved and/or granted Emergency Use Authorization (EUA) by the Food and Drug Administration (FDA) and vaccines on the Recommended Child and Adolescent Immunization Schedule, including co-administered vaccines are monitored through robust FDA and CDC systems that monitor vaccine safety in the United States. This vaccine safety system includes the Vaccine Adverse Event Reporting System (VAERS), Vaccine Safety Data Link (VSD), Clinical Immunization Safety Assessment (CISA), and V-SAFE, a new smartphone-based system added to the safety monitoring system specifically to monitor for side effects of the COVID-19 vaccines. These systems have proven that they work in picking up a safety signal for an extraordinarily rare complication with the Janssen COVID-19 vaccine. VAERS and VSD are specifically designed to monitor safety signals from simultaneous administration of multiple vaccines (ie co-administration).

Q: If I am up to date on COVID-19 vaccine, do I have to quarantine if I have a prolonged exposure to a person who is confirmed positive for SARS-CoV-2?

A: In addition to preventing serious illness and death, growing data show that individuals who are up to date on COVID-19 vaccines can still transmit the virus to others. Individuals who are up to date on their COVID-19 vaccines do not need to quarantine following close contact with someone with COVID-19. However, it is recommended that they wear a well-fitting face mask around others for 10 days from the last date of close contact and that they are tested at least 5 days after last close contact. If the test is positive for COVID-19 or if they are experiencing symptoms in the past 10 days, vaccinated persons should follow recommendations for isolation.

CDC Guidance on Quarantine and Isolation