IMMUNOGENICITY – Expansion of the EUA was based on the results of an immunogenicity trial (summarized in the FDA Fact Sheet) in 67 children 5-11 years old who received a booster dose of the Pfizer vaccine 7-9 months after completing a 2-dose primary series. Geometric mean neutralizing antibody titer (GMT) levels against an ancestral reference strain of SARS-CoV-2 were about 10-fold higher 1 month after the booster dose than they were before it. In a population subset, GMT levels against an Omicron variant of SARS-CoV-2 (B.1.1.529) were about 22-fold higher 1 month after the booster dose than they were 1 month after the second primary-series dose.2

SAFETY – In a safety trial in 371 children 5-11 years old (summarized in the FDA Fact Sheet), injection-site pain, swelling, and erythema, fatigue, headache, muscle pain, and chills were common following administration of a booster dose of the Pfizer vaccine. The rates of these adverse effects were similar to those with primary-series doses of the vaccine. Most adverse effects were mild to moderate in severity.2

DOSAGE AND ADMINISTRATION – In children 5-11 years old, the booster dose of the Pfizer vaccine is the same as the dose for primary immunization (10 mcg IM). A single booster dose may be given ≥5 months after completion of a 2-dose or, in moderately or severely immunocompromised children, a 3-dose primary series.2