Efficacy, effectiveness, and safety of respiratory syncytial virus vaccines in adults: Evidence from clinical trials and real-world effectiveness studies

ABSTRACT

Respiratory syncytial virus (RSV) is an important and under-recognized cause of acute respiratory infection in adults, with disproportionate morbidity and mortality among older adults and individuals with chronic cardiopulmonary diseases. Global and regional burden estimates demonstrate that RSV contributes substantially to hospitalizations and deaths, highlighting the need for effective prevention strategies. Following decades without licensed options for adults, several RSV vaccines have recently completed late-phase clinical trials and entered clinical use. This narrative review synthesizes data on RSV vaccine efficacy, real-world effectiveness, and safety in adults aged 60 years or older and clinically vulnerable populations, including those with chronic medical conditions and immunocompromised states. Across clinical trials, RSV vaccines consistently demonstrated meaningful efficacy against RSV-associated lower respiratory tract disease, with higher protection against severe disease and evidence of persistence across multiple RSV seasons, although attenuation over time was observed. Safety data from randomized trials showed increased reactogenicity without major serious adverse events, whereas post-licensure surveillance identified small excess risks of rare neurologic events. Overall, current RSV vaccines provide clinically important protection against severe RSV disease in older adults, with ongoing research needed to optimize use in high-risk populations.

Keywords: Respiratory syncytial virus, vaccine, vaccine efficacy, vaccine effectiveness, safety