For adults aged 65 and over, a new study offers compelling evidence that vaccination against respiratory syncytial virus (RSV) significantly reduces the risk of serious cardiovascular events. Researchers found that the RSV vaccine provides approximately 79% protection against thromboembolic events – including heart attack, stroke, and venous thromboembolism – associated with RSV infection during the same vaccination season. This finding underscores the growing understanding of RSV’s impact beyond the typical respiratory illness it causes, particularly in older adults.
The link between respiratory viruses like RSV and increased cardiovascular risk has been gaining attention in recent years. Approximately 22% of adults over 50 hospitalized with RSV also experienced an acute cardiac event, highlighting the potential for severe complications. This new research, published in Emerging Infectious Diseases, aimed to quantify the protective effect of vaccination against these potentially life-threatening events. Understanding the benefits of RSV vaccination is particularly important as the virus causes seasonal epidemics, typically from mid-October to early February.
Study Details and Methodology
The retrospective cohort study analyzed data from over 15.5 million Medicare beneficiaries aged 65 and older. Researchers followed participants from October 1, 2023, to March 30, 2024, tracking the occurrence of thromboembolic events – heart attack, ischemic stroke, or venous thromboembolism – within 7 to 30 days of a confirmed RSV diagnosis. Vaccination status was determined based on records, with a 14-day waiting period after vaccination before protection was considered effective. To minimize bias, the study employed a statistical technique called inverse probability of treatment weighting (IPTW), accounting for potential differences between vaccinated and unvaccinated groups.
The study population was diverse, with 58% female, 80% residing in urban areas, and 13% identified as immunocompromised. This broad representation strengthens the generalizability of the findings. Researchers also extended the follow-up period to October 6, 2024, to assess vaccine effectiveness over a longer timeframe and analyzed data during peak RSV circulation periods.
Key Findings on Vaccine Effectiveness
The overall vaccine effectiveness (VE) against RSV-associated thromboembolic events was estimated at 79% (95% confidence interval: 74%-83%). This high level of protection was observed across different subgroups. Among immunocompromised individuals, VE was 69% (95% CI: 56%-78%), while those with healthy immune systems experienced an even higher VE of 82% (95% CI: 77%-86%). This difference was not statistically significant, suggesting consistent protection regardless of immune status.
Age also didn’t appear to significantly impact vaccine effectiveness. VE was 75% (95% CI: 63%-83%) for those aged 65-74 and 80% (95% CI: 74%-84%) for those over 75. Importantly, the protective effect remained relatively stable over time, with VE ranging from 80% (95% CI: 72%-86%) within 14-59 days of vaccination to 75% (95% CI: 60%-84%) after more than 120 days.
The study also compared the effectiveness of two available RSV vaccines, Arexvy and Abrysvo. Arexvy demonstrated a VE of 76% (95% CI: 70%-81%), while Abrysvo showed a slightly higher VE of 85% (95% CI: 77%-90%). However, this difference was not statistically significant, indicating both vaccines offer substantial protection.
Broader Implications and Future Research
While the study focused on RSV-associated thromboembolic events, researchers also examined the vaccine’s effectiveness against all thromboembolic events, regardless of a prior RSV diagnosis. The VE in this broader category was lower, at 21% (95% CI: 19%-22%), which was expected. The authors acknowledge that residual bias may persist due to inherent differences between vaccinated and unvaccinated groups, and that misclassification of events could also play a role.
The findings have important implications for public health recommendations regarding RSV vaccination for older adults. Given the significant risk of cardiovascular complications associated with RSV infection, and the demonstrated effectiveness of vaccination in preventing these events, expanding vaccine access and encouraging uptake could substantially reduce morbidity and mortality. The French health authority, ANSM, has been investigating the use of these vaccines, including ABRYSVO, as reported in a report from November 27, 2025.
Researchers will continue to monitor the long-term effectiveness of RSV vaccines and investigate potential mechanisms underlying the link between RSV infection and cardiovascular events. The next key data point will be the release of further analyses examining the impact of vaccination during subsequent RSV seasons.
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Disclaimer: This article provides information for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
