The 2 RSV vaccines approved in 2023 for adults aged 60 years or older (Arexvy, GSK and Abrysvo, Pfizer) have demonstrated¹ effectiveness in preventing related hospitalizations over 2 seasons, although wiht some waning in the second year after vaccination and significantly lower effectiveness in immunocompromised adults and those with cardiovascular disease.

A third vaccine (mRESVIA, Moderna) was recommended for use in June 2024 but had insufficient uptake for this study period and so “remains a critical data gap”, the investigators point out.

“As RSV vaccine policy for adults evolves, ongoing monitoring of RSV VE (vaccine effectiveness) during subsequent seasons is needed to more fully characterize waning of protection and to inform revaccination intervals,” advised Diya Surie, MD, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, GA, and colleagues.

The investigators accessed the Investigating Respiratory Viruses in the Acutely Ill (IVY) Network to identify older adults hospitalized for acute respiratory illness during the seasons of October 1, 2023-March 31, 2024 or October 1, 2024-April 30, 2025. The cohort was drawn from those who had received clinical testing for RSV, SARS-CoV-2, or influenza within 10 days of illness onset and 3 days of hospital admission.

In the test-negative, case-control study, the case patients (n=821) had tested positive for RSV only, while control patients (n=6,137) tested negative for each condition.RSV vaccine had been administered to 63 of the case patients and 966 of the control group, with most vaccinated during the 2023-2024 season. The primary outcome of the study was hospitalization;