mRNA-based seasonal influenza and SARS-CoV-2 multicomponent vaccine in healthy adults: a phase 1/2 trial.

A multicomponent vaccine targeting several seasonal respiratory pathogens may provide simultaneous protection in a single-injection regimen. We present interim (28 days) findings from a phase 1/2 study of an mRNA-based multicomponent vaccine (mRNA-1083), encoding seasonal influenza and SARS-CoV-2 antigens. Adults (18-79 years) were randomly assigned to receive different compositions of mRNA-1083 at varying dose levels on day 1. The primary study objectives were reactogenicity through 7 days and safety through 28 days postvaccination, and the secondary study objective was immunogenicity against vaccine-matched influenza and SARS-CoV-2 strains at day 29 assessed by hemagglutination inhibition and pseudovirus neutralization assays, respectively. The multicomponent mRNA-1083 vaccine was generally well-tolerated, with most solicited adverse reactions being Grade 1 or 2 in severity. The incidence of unsolicited adverse events was similar across vaccine groups. mRNA-1083 induced immune responses against influenza and SARS-CoV-2 that were, in general, similar to or higher than those achieved with licensed quadrivalent influenza (standard or high dose) and SARS-CoV-2 (bivalent mRNA-1273) vaccines. These data support ongoing phase 3 evaluation of the mRNA-1083 vaccine. ClinicalTrials.gov registration: NCT05827926 .