COVID Bivalent Boosters

About COVID Bivalent Boosters

Bivalent COVID boosters targeting the original strain and BA 4/BA 5 were authorized by the FDA in August 2022. The decision was based on immunogenicity data from mice and humans, not clinical efficacy trials. This represented a new approach to vaccine updates, similar to the annual influenza vaccine process. Observational studies found the bivalent vaccines provided additional protection against symptomatic infection and severe outcomes, which waned over several months. Uptake was low, with fewer than one in five eligible Americans receiving a bivalent dose by the end of 2022. In 2023, the FDA moved to monovalent XBB 1 5 vaccines, dropping the original strain. In 2024, the FDA authorized JN 1 targeted vaccines. The annual update model faces challenges including the rapid evolution of SARS CoV 2 outpacing vaccine development and the phenomenon of immune imprinting, where prior vaccination biases the immune response toward older variants.