Respiratory syncytial virus (RSV) vaccine effectiveness and antibody correlates of protection among older adults in the Community Vaccine Effectiveness (CoVE) observational study.

BackgroundThe first RSV vaccines for adults 60 years and older were approved prior to the 2023-2024 respiratory virus season. This study used data from adults 60 years and older, enrolled into the Community Vaccine Effectiveness (CoVE) cohort study, in Michigan, U.S.A, to evaluate RSV vaccine effectiveness (VE) and antibody correlates of protection. MethodsA Cox proportional hazards model was used to compare incidence of symptomatic / all RSV infections in those vaccinated versus unvaccinated. RSV-specific (preF) binding antibodies were measured in serum specimens and assessed longitudinally. A correlates of protection analysis was conducted using logistic regression. FindingsOf the 281 participants (n=117 vaccinated) enrolled (August 1, 2023, to March 1, 2024), 14 tested positive for RSV. Adjusted RSV VE against any RSV infection was 50.8% (95%CI: -79.1% to 86.5%), and 59.8% (95%CI: -105.2% to 92.1%) against symptomatic RSV. There were 61.2 (95%CI: 16.9, 163.2) RSV infections per 1,000 person-years among vaccinated participants compared to 165.8 infections (95%CI: 88.0, 287.0) per 1,000 person-years among those unvaccinated. A 31% decrease in odds (OR: 0.69, 95% CI: 0.44 to 1.07) of RSV infection per 2-fold increase in antibody concentration was observed. InterpretationRSV infection risk was lower among those with higher antibody titers. RSV incidence was lowest among vaccinated adults, but not significantly. Continued monitoring of reduction of RSV infection in years following vaccination is warranted. FundingNational Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention (75D30122C13149) and National Institute of Allergy and Infectious Diseases (75N93021C00015). The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the Centers for Disease Control and Prevention.