On Mar. 14, 2023, the U.S. Food and Drug Administration (FDA) amended the emergency use authorization (EUA) of the Pfizer-BioNTech COVID-19 Vaccine, Bivalent to provide for a single booster dose of the vaccine in children 6 months through 4 years of age at least 2 months after completion of primary vaccination with three doses of the monovalent (single strain) Pfizer-BioNTech COVID-19 Vaccine.

For the authorization of a single booster dose of the Pfizer COVID-19 Vaccine, Bivalent for children 6 months through 4 years of age at least 2 months after completion of primary vaccination with three doses of the monovalent Pfizer-BioNTech COVID-19 Vaccine, the FDA evaluated immune response data from 60 children in this age group who had completed primary vaccination with three doses of monovalent Pfizer-BioNTech COVID-19 Vaccine and received a booster dose of Pfizer-BioNTech COVID-19 Vaccine, Bivalent in a clinical study. One month after receiving the Pfizer-BioNTech COVID-19 Vaccine, Bivalent, the study participants demonstrated an immune response to both the original SARS-CoV-2 virus strain and to omicron BA.4/BA.5.

In addition, the authorization is supported by the FDA’s previous analyses of the effectiveness of primary vaccination with the monovalent Pfizer-BioNTech COVID-19 Vaccine in individuals 16 years of age and older and individuals 6 months through 4 years of age, and previous analyses of immune response data in adults greater than 55 years of age who had received one booster dose with an investigational Pfizer-BioNTech bivalent COVID-19 vaccine (original and omicron BA.1).