Subject terms
infection
CORONAVIRUS, INFECTION, VIRUS, SEVERE ACUTE RESPIRATORY SYNDROME
Vaccine protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection wanes over time, requiring updated boosters. In a phase 2, open-label, randomized clinical trial with sequentially enrolled stages at 22 US sites, we assessed safety and immunogenicity of a second boost with monovalent or bivalent variant vaccines from mRNA and protein-based platforms targeting wild-type, Beta, Delta and Omicron BA.1 spike antigens. The primary outcome was pseudovirus neutralization titers at 50% inhibitory dilution (IDAnalysis of antibody responses to COVID-19 vaccines encoding variant-specific spike, with or without ancestral spike, suggests no loss of neutralization of the ancestral virus with variant-only vaccines, which may simplify future vaccine updates.