Bivalent Omicron BA.1–Adapted BNT162b2 Booster in Adults Older than 55 Years

BACKGROUND: The emergence of immune-escape variants of severe acute respiratory syndrome coronavirus 2 warrants the use of sequence-adapted vaccines to provide protection against coronavirus disease 2019. METHODS: ] against BA.1) and noninferiority (with respect to seroresponse) of the BA.1-adapted vaccines to BNT162b2 (30 μg). A secondary objective was to determine noninferiority of bivalent BA.1 to BNT162b2 (30 μg) with respect to neutralizing activity against the ancestral strain. Exploratory analyses assessed immune responses against omicron BA.4, BA.5, and BA.2.75 subvariants. RESULTS: GMRs of 0.99 (95% CI, 0.82 to 1.20) and 1.30 (95% CI, 1.07 to 1.58), respectively. BA.4-BA.5 and BA.2.75 neutralizing titers were numerically higher with 30-μg bivalent BA.1 than with 30-μg BNT162b2. The safety profile of either dose of monovalent or bivalent BA.1 was similar to that of BNT162b2 (30 μg). Adverse events were more common in the 30-μg monovalent-BA.1 (8.5%) and 60-μg bivalent-BA.1 (10.4%) groups than in the other groups (3.6 to 6.6%). CONCLUSIONS: The candidate monovalent or bivalent omicron BA.1-adapted vaccines had a safety profile similar to that of BNT162b2 (30 μg), induced substantial neutralizing responses against ancestral and omicron BA.1 strains, and, to a lesser extent, neutralized BA.4, BA.5, and BA.2.75 strains. (Funded by BioNTech and Pfizer; ClinicalTrials.gov number, NCT04955626.).