Safety and immunogenicity of mRNA-1345 revaccination at least 12 months following primary vaccination with a licensed protein subunit RSV vaccine.

Protection from a single RSV vaccine dose is not lifelong, and revaccination may be needed to maintain it. This ongoing, phase 3, open-label trial evaluated revaccination with the RSV vaccine mRNA-1345 ≥12 months after primary vaccination with licensed protein subunit RSV vaccine in adults aged ≥60 years. Primary objectives were safety and immunogenicity. A total of 507 participants were enrolled. Revaccination was well-tolerated, with no safety concerns identified. Robust increases in RSV-A and RSV-B neutralizing antibody geometric mean titers were observed at Day 29. In a post hoc comparison of Day 29 titers following heterologous revaccination with those following primary mRNA-1345 vaccination in a subset of the pivotal efficacy study, geometric mean ratios for RSV-A and RSV-B were 0.952 (95% CI, 0.847-1.070) and 1.087 (95% CI, 0.964-1.226), respectively. These findings support revaccination with mRNA-1345 administered ≥12 months after primary vaccination with a licensed RSV protein subunit vaccine. TRIAL REGISTRATION: NCT07117487.