The study evaluated the humoral immunogenicity of the mRNA-1345 vaccine in older adults (≥60 years) following a single dose. The trial, ConquerRSV, was a randomized, double-blind, placebo-controlled phase 2/3 study. Participants were randomly assigned to receive either the mRNA-1345 vaccine (50 μg encoding prefusion F glycoprotein) or a placebo. Neutralizing antibody (nAb) and pref binding antibody (bAb) levels were assessed at baseline and day 29 post-vaccination in a per-protocol immunogenicity subset (PPIs). Key findings include: - Day 29 nAb geometric mean titers (GMTs) increased 8.4-fold against RSV-A and 5.1-fold against RSV-B from baseline. - Seroreponses (4-fold rise from baseline) in the mRNA-1345 groups were 74.2% and 56.5% for RSV-A and RSV-B, respectively. - Baseline GMTs were lower among participants who met the seroreponse criteria than those who did not. - mRNA-1345 induced pref bAbs at day 29, with a pattern similar to nAbs. - Day 29 antibody responses across demographic and risk subgroups were generally consistent with the overall PPIs. The study concluded that mRNA-1345 enhanced RSV-A and RSV-B nAbs and pref bAbs in adults (≥60 years) across various subgroups, including those at risk for severe disease, consistent with its demonstrated efficacy in preventing RSV disease.The study evaluated the humoral immunogenicity of the mRNA-1345 vaccine in older adults (≥60 years) following a single dose. The trial, ConquerRSV, was a randomized, double-blind, placebo-controlled phase 2/3 study. Participants were randomly assigned to receive either the mRNA-1345 vaccine (50 μg encoding prefusion F glycoprotein) or a placebo. Neutralizing antibody (nAb) and pref binding antibody (bAb) levels were assessed at baseline and day 29 post-vaccination in a per-protocol immunogenicity subset (PPIs). Key findings include: - Day 29 nAb geometric mean titers (GMTs) increased 8.4-fold against RSV-A and 5.1-fold against RSV-B from baseline. - Seroreponses (4-fold rise from baseline) in the mRNA-1345 groups were 74.2% and 56.5% for RSV-A and RSV-B, respectively. - Baseline GMTs were lower among participants who met the seroreponse criteria than those who did not. - mRNA-1345 induced pref bAbs at day 29, with a pattern similar to nAbs. - Day 29 antibody responses across demographic and risk subgroups were generally consistent with the overall PPIs. The study concluded that mRNA-1345 enhanced RSV-A and RSV-B nAbs and pref bAbs in adults (≥60 years) across various subgroups, including those at risk for severe disease, consistent with its demonstrated efficacy in preventing RSV disease.