RSV Immunizations Linked to Lower Severe Disease Risk

A systematic review published in JAMA found respiratory syncytial virus (RSV) vaccines and monoclonal antibodies were associated with reduced risks of severe RSV and related hospitalization among older adults, immunocompromised people, and infants. Evidence also suggested vaccine effectiveness in older adults may decline in later respiratory seasons.

Investigators searched 4 databases from August 1, 2025, through June 29, 2026, for studies of US-licensed RSV vaccines, long-acting monoclonal antibodies, or US epidemiology. They identified 75 eligible studies: 12 randomized clinical trials, 33 comparative observational studies, 16 observational product safety studies without a comparator, and 14 descriptive epidemiologic studies.

In the open-label DAN-RSV randomized trial, single-season RSVpreF (Abrysvo, Pfizer) vaccine effectiveness against RSV-related hospitalization was 83.3% among adults aged 60 years or older (95% CI, 42.9%-96.9%). In a retrospective cohort, effectiveness against hospitalization decreased significantly from 81.1% during 0 to 6 months after vaccination to 48.5% during 12 to 18 months follow-up.

After maternal RSVpreF vaccination between 32 and 36 weeks’ gestation, effectiveness against infant RSV-related hospitalization ranged from 51.0% to 70.0%. Nirsevimab (Beyfortus, Sanofi) effectiveness against hospitalization among infants and children ranged from 63.6% to 93.0%; effectiveness against RSV-related intensive care unit admission ranged from 76.0% to 89.6%.

No new safety concerns were identified. Three randomized trials reported no Guillain-Barré syndrome among 132,243 participants, although one self-controlled case series in older adults suggested a possible increase within 42 days after vaccination. Comparative studies found no significant association between vaccination during pregnancy and preterm birth or other adverse pregnancy outcomes. The authors cautioned that many studies had substantial potential for bias and that the short search window limited evidence for some outcomes and subgroups.

Source: Senerth E, Sheikholeslamian SM, Babatunde I, et al. RSV immunization effectiveness and safety for the 2026-2027 respiratory season. JAMA. Published online September 2, 2026. doi:10.1001/jama.2026.17871