Immunogenicity, reactogenicity, and safety of an mRNA-based seasonal influenza and SARS-CoV-2 multicomponent vaccine, mRNA-1083, in adults aged ≥50 years in Japan

A multicomponent vaccine targeting seasonal influenza and coronavirus disease 2019 (COVID-19) may reduce disease burden by providing simultaneous protection in a single injection. We report findings from Part 1 (Japan) of a phase 3, Asia-Pacific, randomized, observer-blind study evaluating immunogenicity, reactogenicity, and safety of mRNA-based multicomponent vaccine mRNA-1083, combining influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens. Participants aged ≥50 years were randomized (1:1) to receive mRNA-1083 + placebo or Japan-licensed influenza hemagglutinin (HA) vaccine + mRNA-1273. Overall, 2022 participants were randomized, and 2013 received study intervention. At Day 29, mRNA-1083 elicited noninferior immune responses versus active comparators for all evaluated influenza strains and SARS-CoV-2. Among high-risk participants (aged ≥65 years and 60 to