Three Doses of Pfizer-BioNTech COVID-19 Vaccine is Efficacious in Young Children

A three-dose primary series of 3-μg BNT162b2 (Pfizer-BioNTech) COVID-19 vaccine was found to be safe, immunogenic, and efficacious in children 6 months to 4 years of age, according to a new study.

The study’s results were published in The New England Journal of Medicine.

Overall, a vaccine efficacy of 73.2% was observed in individuals 6 months to 4 years of age. In children ages 6 months to less than 2 years of age, the vaccine demonstrated a 75.8% efficacy, and among children 2 to 4 years of age it was 71.8% efficacious.

In the phase 2–3 trial, participants were randomly assigned (in a 2:1 ratio) to receive two 3-μg doses of BNT162b2 or placebo. The participants included 1178 children 6 months to less than 2 years of age, and 1835 children 2 to 4 years of age who received the Pfizer-BioNTech vaccine, and 598 and 915, respectively, received placebo.

The investigators administered two 3-μg BNT162b2 doses 21 days apart followed by a third dose given at least 8 weeks later.

“On the basis of preliminary immunogenicity results, a third 3-μg dose (≥8 weeks after dose 2) was administered starting in January 2022, which coincided with the emergence of the B.1.1.529 (Omicron) variant,” the investigators wrote. “Immune responses at 1 month after doses 2 and 3 in children 6 months to less than 2 years of age and those 2 to 4 years of age were immunologically bridged to responses after dose 2 in persons 16 to 25 years of age who received 30 μg of BNT162b2 in the pivotal trial.”

The vaccines were reported to be safe and immunogenic in children 6 months to 4 years of age.

“Immunobridging success criteria for the geometric mean ratio and seroresponse at 1 month after dose 3 were met in both age groups. BNT162b2 reactogenicity events were mostly mild to moderate, with no grade 4 events. Low, similar incidences of fever were reported after receipt of BNT162b2 (7% among children 6 months to <2 years of age and 5% among those 2 to 4 years of age) and placebo (6 to 7% among children 6 months to <2 years of age and 4 to 5% among those 2 to 4 years of age),” the investigators wrote.

The investigators said limitations included that the study did not assess efficacy against severe disease or against specific SARS-CoV-2 variants. The investigators lacked data on Omicron BA4 and BA5 serum-neutralizing activity and longer-term follow-up to assess immune-response duration as well as safety. In addition, the trial population was predominantly White participants.

“These data support vaccination of children 6 months to 4 years of age with three 3-μg primary BNT162b2 doses,” the authors concluded.