Bivalent Covid-19 Vaccines — A Cautionary Tale

This perspective by Paul A. Offit critically examines the development and deployment of bivalent mRNA Covid-19 vaccines designed to target Omicron variants BA.4 and BA.5. It recounts the timeline of variant emergence, vaccine adaptations, and policymaking in the U.S., noting that bivalent boosters did not significantly improve immunogenicity compared to monovalent boosters. Offit highlights the concept of immune imprinting as a key reason for the limited efficacy, and argues that boosters should focus on protecting vulnerable populations rather than preventing all symptomatic infections. The article calls for reevaluating booster strategies as virus strains rapidly evolve.

This perspective by Paul A. Offit critically examines the development and deployment of bivalent mRNA Covid-19 vaccines designed to target Omicron variants BA.4 and BA.5. It recounts the timeline of variant emergence, vaccine adaptations, and policymaking in the U.S., noting that bivalent boosters did not significantly improve immunogenicity compared to monovalent boosters. Offit highlights the concept of immune imprinting as a key reason for the limited efficacy, and argues that boosters should focus on protecting vulnerable populations rather than preventing all symptomatic infections. The article calls for reevaluating booster strategies as virus strains rapidly evolve.