Molecular characterization of RSV infections in elderly patients during the 2023/2024 season in the era of nirsevimab introduction.

Abstract

RSV can cause severe infections in the elderly. Nirsevimab is a novel prophylactic monoclonal antibody, widely used in infants in France during the 2023/2024 season. It may select for resistant RSV variants that, if transmitted in the community, could compromise vaccine efficacy in the elderly. In this study, we analyzed RSV full-length genomes (68% RSV-A, 32% RSV-B) from 125 patients >60y during 2023/2024 season. Genetic diversity of RSV-F was low, with no resistance-associated substitutions (RASs) detected. While no RASs were identified, ongoing monitoring is essential to prevent the emergence of resistant variants that could affect vaccine efficacy in the elderly.