The FDA has announced significant updates to its COVID-19 vaccination strategy, authorizing a second bivalent booster dose for specific high-risk groups and streamlining the overall vaccination process. These changes aim to improve protection against current and emerging variants while simplifying vaccine recommendations for the general population.
Authorization of Second Bivalent Booster Dose
Individuals aged 65 and older are now eligible for a second dose of the bivalent COVID-19 vaccine, administered at least 4 months after their initial bivalent dose. This decision is supported by data indicating that immunity wanes over time in this population, and an additional dose can restore protection. Immunocompromised individuals are also eligible for a second bivalent dose, given at least 2 months after their first, with the possibility of further doses at the discretion of their healthcare provider.
Streamlining Vaccination Strategy
The FDA has fully replaced the monovalent Moderna and Pfizer-BioNTech mRNA vaccines with the updated bivalent boosters, which target both the original SARS-CoV-2 strain and the Omicron BA.4/BA.5 subvariants. This harmonization applies to all doses for individuals aged 6 months and older. The emergency use authorizations (EUAs) for the monovalent vaccines have been scrapped.
For unvaccinated adults and children, a single dose of the bivalent vaccine will now suffice as the initial vaccination, rather than the previously recommended two doses of the monovalent vaccines. This simplified approach aims to increase vaccination coverage across the country. The FDA's Peter Marks, MD, PhD, noted that most of the U.S. population 5 years of age and older have antibodies to SARS-CoV-2 due to either vaccination or prior infection, supporting the decision to simplify the vaccination schedule.
Data Supporting Single Bivalent Dose
FDA analysis of immune response data from two studies supported the effectiveness of a single dose of the bivalent Moderna vaccine. One study involved 145 individuals aged 6 years and older with prior COVID-19 infection, while the other included 1,376 individuals aged 6 years and up without prior infection but who had received two doses of the monovalent vaccine. The data showed that the immune response after one bivalent dose among those with prior infection was comparable to that seen after two monovalent doses among those without prior infection.
Effectiveness of a single dose of the bivalent Pfizer-BioNTech vaccine was in part supported by observational data from England on the effectiveness of one dose of the company's monovalent shot in adolescents, which showed additional protection for those with prior infection versus those without a past infection.
Monitoring Emerging Variants
The FDA is closely monitoring emerging variants, including XBB.1.9.1 (Hyperion) and XBB.1.16 (Arcturus), which each account for approximately 7% of cases. While the current bivalent vaccine appears to help prevent severe disease from XBB.1.5 infections, the agency intends to discuss future vaccination strategies at a Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting in June to address these evolving variants.
