The COVID-19 vaccines for children have the same active ingredients as the primary vaccines given to adults. However, children receive a smaller, age-appropriate dose that is the right size for them. Clinical trial data showed that a smaller dose for children produced a strong immune response (very similar to that of adults) and caused fewer side effects than an adult dose.
For booster vaccination, CDC recommends eligible people 6 months and older receive an age-appropriate, updated Pfizer or Moderna vaccine that offers better protection against variants. For children age 6 months to 4 years who get the Pfizer primary series, the updated bivalent vaccine will be used as the third dose in the series, rather than as a separate booster. Children in this age group who previously received 3 monovalent Pfizer primary series doses are eligible to receive 1 bivalent Pfizer booster dose at least 2 months after completion of the monovalent primary series.
For more information about the safety, efficacy, and timing of each pediatric vaccine, please visit CDC’s page about COVID-19 Vaccines for Children and Teens.