A recent study published in The Lancet Infectious Diseases confirms the high effectiveness of respiratory syncytial virus (RSV) vaccines in preventing infection and severe illness among older adults. The real-world analysis, focusing on US veterans, demonstrated that RSV vaccines are 78% to 80% effective against RSV infection, emergency department/urgent care (ED/UC) visits, and hospitalization during the 2023-2024 respiratory virus season. These findings reinforce the importance of RSV vaccination for individuals aged 60 years and older.
Key Findings on Vaccine Effectiveness
The study, led by researchers at the Veterans Affairs Portland Health Care System, emulated a target trial using electronic health records from the Veterans Health Administration (VHA). It compared outcomes between vaccinated (with either RSVPreF3 [Arexvy] or RSVpreF [Abrysvo]) and unvaccinated veterans aged 60 years and older from September through December 2023, with follow-up until March 2024. The results indicated:
- RSV Infection: Estimated vaccine effectiveness (VE) was 78.1% (95% CI, 72.6% to 83.5%).
- ED/UC Visits: VE was 78.7% (95% CI, 72.2% to 84.8%) against RSV-related emergency department and urgent care visits.
- Hospital Admission: VE was 80.3% (65.8% to 90.1%) against hospital admission due to RSV.
Notably, the study also assessed vaccine effectiveness in high-risk subgroups, revealing that among veterans aged 80 years and older, VE against RSV infection was 72.3% (57.9% to 84.6%), and in those with weakened immune systems, it was 71.6% (55.4% to 85.2%).
Clinical Significance and Impact
During the study period, the incidence of RSV infection was significantly lower in vaccinated participants (1.7 events per 1,000 person-years) compared to unvaccinated individuals (7.3 per 1,000 person-years). Similarly, RSV-related ED/UC visits and hospitalizations were reduced in the vaccinated group. There were no intensive care unit (ICU) admissions or deaths among vaccinated participants, while the unvaccinated group experienced 0.2 ICU admissions and 0.1 deaths per 1,000 person-years.
These findings underscore the clinical benefits of RSV vaccination, particularly for older adults and those with underlying health conditions. According to Amanda B. Payne, PhD, from the CDC, “For adults ages 60 and older, RSV vaccines reduced the likelihood of RSV-associated hospitalizations by 80%, critical illness by 81%, and emergency department encounters by 77% compared to not receiving an RSV vaccine.”
Addressing Unmet Needs and Future Directions
Despite the demonstrated effectiveness, vaccine uptake remains low. By the end of the 2023-2024 respiratory illness season, only 24% of eligible adults in the USA had received an RSV vaccine. Experts emphasize the need for extended follow-up to evaluate the duration of protection and to address remaining questions about optimal vaccination schedules and vaccine effectiveness in diverse populations.
Harish Nair, MBBS, PhD, and Thomas Williams, MB BChir, from the University of Edinburgh, noted that further research is needed to determine the optimal RSV vaccination schedule, VE in women in a real-world setting, and VE against post-RSV ICU admissions, complications, and death.
Updated CDC Guidance
Given the robust evidence supporting RSV vaccine effectiveness, the CDC has updated its guidance for the 2024-2025 respiratory virus season. The updated recommendations clarify who is at highest risk for severe illness and now recommend that all adults ages 75 and older and adults ages 60 to 74 with risk conditions should get an RSV vaccine if they haven’t already received one.
