Longitudinal measurements of respiratory syncytial virus (RSV) immunity over 4 winter seasons reveal that viral neutralization titers, RSV prefusion F protein (pre-F)-specific immunoglobulin M and immunoglobulin G (IgG) levels, and RSV antibody-dependent cellular phagocytosis function gradually returned to prepandemic levels in female healthcare and school workers of childbearing age after 2 winter seasons, following the resurgence of RSV cases in the Vancouver metropolitan region (British Columbia, Canada). In contrast, pre-F IgG avidity profiles remained unchanged. These findings support the notion that repeated viral infections are necessary to maintain high RSV antibody levels in the population.
