The first comprehensive real-world study of respiratory syncytial virus (RSV) vaccination shows robust protection against severe disease requiring hospital care, with effectiveness remaining strong even among vulnerable populations. The Lancet Regional Health study tracked over 100,000 patients across two RSV seasons, providing critical evidence for vaccination programs targeting older adults and immunocompromised individuals.
RSV Vaccine Effectiveness by Population Group
Protection against hospital or emergency department care, first season data
Source: Lancet Regional Health Americas, 2026 | Georgian Medical Journal News
Strong Protection Across Age Groups
The retrospective test-negative case control study analyzed data from Kaiser Permanente Southern California, tracking RSVpreF vaccine effectiveness from September 2023 through May 2025. Dr. Bradley Ackerson, lead researcher at Kaiser Permanente, and colleagues found that vaccination provided 73% protection against RSV-associated hospitalization or emergency department visits among adults aged 60 and older during the first season.
The protection was particularly robust among younger seniors, with 78% effectiveness in the 60-74 age group compared to 69% effectiveness among those 75 and older, according to the study published in Lancet Regional Health Americas. Even among immunocompromised patients, who typically show reduced vaccine responses, effectiveness reached 51% against severe RSV disease.
Modest Decline in Second Season
Vaccine effectiveness showed some decline in the second RSV season, dropping to 68% overall protection among adults 60 and older. The researchers observed more pronounced waning among immunocompromised adults, where effectiveness fell to 35% in the second season.
Despite this decline, the Centers for Disease Control and Prevention notes that these effectiveness levels remain clinically significant for preventing severe outcomes. The study’s two-season follow-up provides the first evidence of RSV vaccine durability in real-world conditions, informing future booster recommendations.
Public Health Impact for Vulnerable Populations
The findings carry particular importance for vulnerable populations who face barriers to healthcare access. RSV causes an estimated 60,000 to 80,000 hospitalizations annually among U.S. adults aged 65 and older, according to CDC surveillance data.
The study’s methodology strengthened confidence in the results by using a test-negative design, comparing vaccinated and unvaccinated patients who sought care for respiratory symptoms but tested negative for RSV. This approach helps control for healthcare-seeking behavior and reduces bias that could inflate effectiveness estimates in observational studies.
RSVpreF vaccination was associated with substantial protection against RSV-associated severe respiratory illness, with effectiveness of 73% overall and 51% even among immunocompromised adults in the first season.
— Dr. Bradley Ackerson, Kaiser Permanente Southern California (Lancet Regional Health Americas, 2026)
Key takeaways
- RSV vaccination provided 73% protection against hospitalization among adults 60+ in first season
- Effectiveness remained at 51% even among immunocompromised patients, a historically difficult-to-protect population
- Protection declined modestly to 68% overall in second season, informing future booster strategies
These real-world effectiveness data support broader RSV vaccination programs for older adults, particularly as health systems prepare for the upcoming respiratory virus season. The study’s evidence of sustained protection across diverse populations, including those with compromised immune systems, strengthens the case for targeted vaccination strategies in global health initiatives and vulnerable communities.
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