Adult RSV Vaccination: What Is the Role of RSV Subgroup in Disease Prevention?

Respiratory syncytial virus (RSV) cocirculates as two antigenic subgroups, RSV A and RSV B, with irregular dominance by season. Despite highly conserved fusion (F) protein epitopes, sequence, and antigenic differences between A and B, especially within prefusion F, can modulate neutralization and susceptibility. First-in-class adult RSV vaccines licensed in 2023 adopt two antigen strategies: monovalent stabilized prefusion F based on sequences from the RSV A subgroup, and bivalent stabilized prefusion F antigens from both RSV A and RSV B subgroups to decrease reliance on RSV A cross-protection. Clinical data from bivalent vaccine studies support high efficacy against disease from both subgroups, while monovalent vaccine studies suggest that RSV B cross-protection may wane more quickly. Emerging and continued real-world vaccine effectiveness monitoring of both monovalent and bivalent RSV vaccines will be needed to assess this early signal.