Abstract: Background Respiratory syncytial virus (RSV) causes substantial respiratory disease. Bivalent RSV prefusion F (RSVpreF) vaccine is licensed in ≥60-year-olds. RSVpreF was well tolerated and immunogenic in a phase 1/2 study. We evaluated antibody persistence after initial vaccination and safety and immunogenicity after revaccination from this study. Methods Healthy adults were randomized to receive initial vaccination and revaccination 12 months later with either placebo or RSVpreF (240 µg with or without aluminum hydroxide). RSV-A and RSV-B geometric mean neutralizing titers (GMTs) were measured through 12 months after both vaccinations. Tolerability and safety were assessed. Results There were 263 participants revaccinated (18–49 years old, n = 134; 65–85 years old, n = 129). Among 18- to 49-year-olds and 65- to 85-year-olds, geometric mean fold rises (GMFRs) for both RSV subgroups (RSV-A, RSV-B) 1 month after initial RSVpreF vaccination were 13.3 to 20.4 and 8.9 to 15.5, respectively, as compared with levels before initial vaccination; corresponding GMFRs 12 months after initial vaccination were 4.1 to 5.0 and 2.6 to 4.1. GMFRs 1 month after revaccination vs levels before revaccination were 1.4 to 2.3 and 1.4 to 2.2 for 18- to 49-year-olds and 65- to 85-year-olds. Peak GMTs after revaccination were lower than those after initial vaccination. GMTs 12 months after initial vaccination and revaccination were similar, with GMFRs ranging from 0.7 to 1.6. No safety signals occurred. Conclusions RSVpreF revaccination was immunogenic and well tolerated among adults. Clinical Trials Registration. NCT03529773 (ClinicalTrials.gov).
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