RSV Vaccines Demonstrate Sustained Effectiveness for Older Adults

This article was originally published on ContagionLive.

The two RSV vaccines approved in 2023 for adults aged 60 years or older (Arexvy, GSK; and Abrysvo, Pfizer) have demonstrated 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.¹

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. An 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 the 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 the 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 it was 68% (52-79%) in those aged 75 years or older. The two vaccines were similarly effective against both RSV subtypes A or B.

They were less effective, 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.

They were also significantly less effective (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.

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.