What You Should Know About COVID-19 Vaccines for Young Children

Child wearing a mask and looking slight off camera

MSK will soon begin offering the Pfizer-BioNTech vaccine to MSK pediatric patients ages 5 through 11.

The Centers for Disease Control and Prevention (CDC) has recommended that children ages 5 through 11 be vaccinated with the Pfizer-BioNTech COVID-19 vaccine (Comirnaty®). The decision follows an emergency use authorization for the vaccine issued on October 29, 2021, by the US Food and Drug Administration (FDA).

According to the CDC, “While COVID-19 tends to be milder in children compared with adults, it can make children very sick and cause children to be hospitalized. In some situations, the complications from infection can lead to death.”

MSK will soon begin offering the Pfizer vaccine to MSK pediatric patients ages 5 through 11.


Memorial Sloan Kettering Chief Medical Epidemiologist Mini Kamboj

Mini Kamboj, MSK’s Chief Medical Epidemiologist

Mini Kamboj, Memorial Sloan Kettering Cancer Center’s Chief Medical Epidemiologist, has answers to your questions about COVID-19 vaccines for children.

Which vaccine can young children receive?

Children ages 5 through 11 are now eligible to be immunized with the Pfizer vaccine. Children 12 and older were already eligible to receive the Pfizer vaccine. Studies on the Moderna and Johnson & Johnson/Janssen (J&J) COVID-19 vaccines are also underway.

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How do I schedule a COVID-19 vaccine for my child if they are an MSK patient?

You can schedule a vaccination by talking to your child’s primary doctor at MSK.

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How do we know the vaccine is safe and effective in this age group?

The vaccine has been tested in an ongoing study of approximately 4,700 children ages 5 through 11, according to the FDA. The vaccine was found to be 90.7% effective in preventing COVID-19 in this group. No serious side effects have been reported in the study.

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Do children with moderate to severe immunosuppression require a third dose of the Pfizer vaccine?

Children 12 years and older who meet eligibility criteria for a third dose can receive the third dose 28 days after the second Pfizer dose. 

At this time, the CDC does not recommend an additional primary dose (third dose) for children ages 5 to 11 with moderate to severe immunosuppression, including cancer treatment. If this changes in the future, we will communicate with our patients and families.

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How is the vaccine dose for young children different from the one for adults?

Children ages 5 through 11 will receive a dose that is one-third the size of an adult dose, delivered with smaller needles and stored in different vials to avoid mix-ups with adult doses. The smaller dose was chosen to minimize side effects while still producing a strong immune response. Children in this age group will receive a second shot three weeks after the first dose.

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Are the side effects in children different from those in adults?

No, the side effects are not different. Children ages 5 through 11 in the trial experienced only mild side effects, which were more frequent after the second dose. The most common were pain at the injection site, fatigue, and headache. Side effects typically occurred within two days after vaccination, and most went away within one to two days.

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If children are at lower risk of serious complications from COVID-19, why should they get vaccinated?

Children are at a lower risk overall of becoming severely ill with COVID-19 compared with adults; however, the CDC also reports children can still become very sick. Like adults, children can also have both short-term and long-term health complications after COVID-19. A rare but serious complication of COVID-19 infection called multisystem inflammatory syndrome in children (MIS-C) is most frequent among children 5 to 11 years of age and can be prevented by vaccination.

Most important, children ages 5 to 11 are at least as likely to be infected as adults and spread COVID-19 to others, including in the household and at school.

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Is there risk from heart problems after the vaccine?

Research has shown that there is a greater risk of heart problems from being infected with COVID-19 than from being vaccinated. 

Studies from Israel and the United States link some COVID-19 vaccines to a rare heart condition called myocarditis or pericarditis (inflammation of the heart muscle or its lining). This complication is primarily seen in young males and has rarely been described in 12- to 15-year-old children after COVID-19 vaccination (estimated 60 cases per million doses). Although the risk of this complication for 5- to 11-year-olds is unknown, it is expected to be even smaller based on the lower likelihood of similar heart problems in general and the use of a lower COVID-19 vaccine dose in this age group. So far, no cases of heart inflammation have been detected in the clinical study of the 5- to 11-year-old age group.

The CDC has a very robust tracking system that closely follows the occurrence of heart inflammation cases following vaccination, and this information is routinely reported on their website and shared with the public.

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What about children younger than 5? Is the vaccine available to them?

Not yet. In children younger than 5, very small doses of the vaccine — one-tenth of the adult dose — are being tested in clinical trials. But not enough data is yet available for this age group to determine effectiveness and safety.

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Should a child who has already had the COVID-19 infection take the vaccine?

Yes, the CDC recommends vaccination for children who have fully recovered from COVID-19 infection. Approximately 9% of children in Pfizer’s clinical trial had evidence of past infection. The vaccine was safe and effective for this group of children and is expected to increase the protection from future infection.

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Can children take the vaccine with other scheduled childhood vaccinations?

Yes, the other vaccines may need to be administered at a different site. No specific time interval is recommended between routine vaccinations and the COVID-19 vaccine for children.

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Is MSK offering COVID-19 vaccines to children of MSK staff, members of the public, or siblings of MSK patients?

No, we are providing the vaccines only to pediatric patients at MSK.

November 5, 2021

Additional Resources

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