Two recent studies add to the growing evidence that respiratory syncytial virus (RSV) vaccination can benefit older adults. A US study of nearly 7,000 adults aged 60 years and older found that RSV vaccination was 58% effective against RSV-associated hospitalizations for two RSV seasons.1 A Danish study found that RSV vaccination reduced both RSV-associated hospitalization and any cardiorespiratory hospitalization among older adults, including those with known cardiovascular disease.2
“Similar to what we have seen with the influenza vaccines, people with a chronic cardiovascular disease are at increased risk of hospitalizations with worsening of their preexisting disease or triggering of new coronary events with respiratory viruses such as flu, RSV, and COVID-19,” said Mats C. Højbjerg Lassen, MD, Research Fellow at the Center for Translational Cardiology and Pragmatic Randomized Trials, University of Copenhagen Gentofte Hospital, Copenhagen, Denmark. “Preventing these acute infections during the winter season may help keep them out of hospital.”
Dr. Lassen was lead author on Bivalent RSV Prefusion F Protein–Based Vaccine for Preventing Cardiovascular Hospitalizations in Older Adults: A Prespecified Analysis of the DAN-RSV Trial.2 A second study, RSV Vaccine Effectiveness Against Hospitalization Among US Adults Aged 60 Years or Older During 2 Seasons, found similar benefits for RSV vaccination on hospitalization for RSV infections.1
The Danish study was a prespecified secondary analysis of the Vaccine Effectiveness of a Bivalent RSV Prefusion F Protein-Based Vaccine for Preventing RSV Hospitalizations in Adults (DAN-RSV) trial examining the effect of RSV vaccination on cardiorespiratory and cardiovascular hospitalizations. The trial included 131,276 adults aged 60 years and older across Denmark who were randomized to receive the RSV vaccine (65,642 patients) or not receive the vaccine (65,634 patients) during the 2024 to 2025 winter season. The mean age of patients was 69.4 years, 50.3% were male, and 21.8% had preexisting cardiovascular disease. The DAN-RSV trial met its primary outcome, showing that the RSV vaccine was 83.3% effective against RSV-associated respiratory hospitalizations during the first season.
Dr. Lassen reported in this secondary analysis that all-cause cardiorespiratory hospitalization was lower in the RSV vaccine group compared with the unvaccinated control group (26.4 vs 29.2 events per 1,000 participant years). There were no significant differences in the rate of all-cause cardiovascular hospitalizations between the groups, although the RSV vaccine group had a numerical advantage (16.4 vs 17.7 events per 1,000 participant years). There were no significant differences in rates of stroke, myocardial infarction, heart failure hospitalization, or atrial fibrillation hospitalization between the groups.
The US study was a test-negative, case-control study conducted across 26 hospitals in 20 states. It included 6,958 adults hospitalized for an acute respiratory illness during the RSV seasons in 2023 to 2024 and 2024 to 2025. Of the entire cohort, 821 case patients (11.8%) had RSV only, and 6,137 control patients (88.2%) tested negative for RSV, COVID-19, and influenza. The median age was 72 years, 50.8% were female, and 26.3% were immunocompromised. Most (62.0%) were White and 20.1% were Black. A total of 7.7% of with patients RSV and 15.7% of control patients had been vaccinated against RSV at least 14 days before the onset of illness.
Investigators determined RSV vaccination was 58% effective against RSV-associated hospitalization during the two seasons, ranging from 69% effective for same-season vaccination to 48% for prior-season vaccination. The estimated effectiveness was significantly lower among patients who were immunocompromised (30%) compared with patients who were not immunocompromised (67%). RSV vaccination was also less effective among those with preexisting cardiovascular disease (56%) compared with those without cardiovascular disease (80%).
The European Society of Cardiology has pointed to vaccination against respiratory viruses, including RSV, as a promising form of cardiovascular protection in individuals at high risk, Dr. Lassen noted, but there are currently no RSV-specific vaccine guidelines among people with cardiovascular disease.
“Flu vaccine is recommended among people with chronic cardiovascular disease,” he said. “We are not there yet with RSV vaccine. We are expanding this season with a larger sample size so we can explore important subgroups of patients—like those with chronic cardiovascular disease, chronic lung disease, diabetes—those sorts of groups who may face a much higher baseline risk of hospitalization and severe outcomes with the virus. Hopefully we can say something more specific about RSV vaccine in these important subgroups after this current winter season.”
References
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(16):1442-1451. doi:10.1001/jama.2025.15896
2. Lassen MCH, Johansen ND, Christensen SH, et al. Bivalent RSV prefusion F protein-based vaccine for preventing cardiovascular hospitalizations in older adults: a prespecified analysis of the DAN-RSV trial. JAMA. 2025;334(16):1431-1441. doi:10.1001/jama.2025.15405
