A recent study evaluated the safety and efficacy of a third BNT162b2 vaccine in children aged six months to 4 years. The BNT162b2 vaccine, developed by Pfizer-BioNTech, has already been approved for use in individuals aged 12 and above and emergency authorization for children aged 5 to 11.
The study was conducted to determine if a third dose of the vaccine could enhance immune responses against the B.1.1.529 (omicron) variant, which has been spreading rapidly and causing severe disease in some populations.
The study’s results, published in the New England Journal of Medicine, showed that the third dose of the BNT162b2 vaccine was safe and well-tolerated in children aged six months to 4 years. The most common side effects were similar to those observed after the first and second doses, including fever, irritability, and injection site reactions. However, the incidence of fever was higher after the third dose than after the second dose.
The study also showed that a third dose of the vaccine significantly increased antibody levels in children aged 2 to 4 years. The antibody levels in this age group after the third dose were similar to those in older children and young adults after the second dose. These findings suggest that a third dose of the BNT162b2 vaccine may be necessary to provide adequate protection against the omicron variant in young children. However, further studies are needed to determine the duration of protection and the vaccine’s long-term safety in this age group.
A three-dose primary series of the Pfizer-BioNTech COVID-19 vaccine is safe and effective in children six months to 4 years old. The study involved the administration of two 3-μg doses of the vaccine 21 days apart, followed by a third dose given at least eight weeks later. Immunogenicity data showed robust immune responses to the vaccine in young children, including successful bridging to young adults from the original adult efficacy study.
\While the immune bridging data after the second dose only partially met success criteria among children aged 2 to 4 years, the exploratory analysis suggested that three 3-μg doses induced neutralizing titers against the omicron BA.1 variant, with response patterns generally similar to those observed in adults aged 18 to 50 years administered a third dose.
The three-dose primary series was found to be 73.2% effective against COVID-19 at least 7 days after the third dose, which was entirely within the omicron-dominant phase. The availability of COVID-19 vaccines for young children is critical, especially given the surge in omicron-related cases and hospitalizations in this age group.
The observed safety profile of the Pfizer-BioNTech COVID-19 vaccine in young children did not raise any concerns. Reactogenicity to the vaccine, which included irritability as an adverse reaction in children aged 6 months to less than 2 years, was primarily mild to moderate and short-lived, with most events occurring at frequencies similar to or lower than those after the third dose as compared with after the first or second dose. No deaths were reported, and few adverse events led to withdrawal.
However, the trial was not powered to assess efficacy against severe disease or specific SARS-CoV-2 variants. Longer-term follow-up is needed to assess immune-response duration as well as safety. The trial population was predominantly White, and the study was not powered to detect potential rare side effects.
Follow-up from this trial and effectiveness and safety data from real-world use should provide further information. These data support the vaccination of children aged 6 months to 4 years with three 3-μg primary doses of the Pfizer-BioNTech COVID-19 vaccine. The vaccine has been granted emergency use authorization for this age group and is recommended by the Centers for Disease Control and Prevention.
