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 with 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; with secondary measures of the severity of hospital course including supplemental oxygen requirement, acute respiratory failure, acute organ failure, intensive care unit admission, and a composite of invasive mechanical ventilation or death.
Surie and colleagues reported that overall effectiveness of the vaccines in preventing RSV-related hospitalizations among all adults aged 60 years or older during 2 seasons was 58% (95% CI, 45-68%).In those 60 to 74 years of age, vaccine effectiveness was 46% (21-63%); and was 68% (52-79%) in those aged 75 years or older. The two vaccines were similarly effective, and against both RSV subtype A or B.
They found significantly lower effectiveness, however, in those with moderate or severe immunocompromise (30%, -9 to 55%) compared with immunocompetent adults (67%, 53-77%)."These findings suggest that patients with moderate to severe immunocompromise may have both lower initial immune responses to RSV vaccination and less durable ones that might require a shorter revaccination interval," Surie and colleagues indicate.
There was also significantly lower effectiveness (56%, 32-72%) for those immunocompetent adults with cardiovascular disease--most with heart failure, than those without cardiovascular disease (80%, 62-90%).The investigators posit that proinflammatory states that accompany heart disease may diminish immune response, contributing to both increased susceptibility to RSV and potentially inhibited immune response to vaccination.
What You Need to Know
RSV vaccines for adults ≥60 were moderately effective (overall 58%) at preventing hospitalization across two seasons, with better protection in those ≥75 years but reduced effectiveness in immunocompromised adults and those with cardiovascular disease.
Early evidence suggests protection may wane by the second season after vaccination, indicating that some groups—especially immunocompromised individuals—may benefit from shorter revaccination intervals.
As adult RSV vaccine policy evolves, ongoing monitoring and further data—particularly for newer vaccines like mRESVIA—are needed to refine dosing intervals and identify populations requiring enhanced protection.
The investigators noted some waning of effectiveness, albeit not statistically significant, in the second year after vaccination. Among all adults aged 60 years or older, vaccine effectiveness was 69% (52-81%) against hospitalization when vaccination was administered in the same season as illness onset, compared to 48% (27-63%) in the second season after vaccination. This possible waning of protection, they suggest, could warrant shorter revaccination intervals
While Surie and colleagues found that a single dose of RSV vaccine provided protection against related hospitalization and severe in-hospital outcomes through 2 seasons, they advise additional study of those with less robust response."Early findings suggest certain subpopulations, including adults with immunocompromise and those with cardiovascular disease, may require additional doses of RSV vaccine earlier than those without these conditions."
Reference
1. Surie D, Self WH, Yuengling KA, et al. RSV vaccine effectiveness against hospitalization among US adults aged 60 years or older during 2 seasons. JAMA. 2025:334:1442-1451.
