TOPLINE:

The respiratory syncytial virus prefusion F protein (RSVpreF) vaccine was highly effective against RSV-related acute respiratory illness (ARI) requiring emergency care or hospitalization, including in seniors who required severe oxygen support and those aged 75 years or older.

METHODOLOGY:

• Researchers conducted a retrospective case-control study to assess the effectiveness of the RSVpreF vaccine against ARI in older adults.
• The study included patients aged 60 years or older (54.7% women) who presented to Kaiser Permanente Southern California (KPSC) with ARI requiring an emergency department (ED) visit or hospitalization.
• Case patients (n = 695) included those who tested positive for RSV, whereas control individuals were classified as either “strict” (n = 1034) or “broad” (n = 8270) control individuals.
• “Strict” control individuals tested negative for RSV, influenza, and other vaccine-preventable pathogens but positive for one or more nonvaccine-preventable pathogens. “Broad” control individuals comprised of all individuals who tested negative for RSV.
• Vaccine effectiveness (VE) was estimated for ED visits and hospitalizations overall and across subgroups defined by age (≥ 75 years or ≥ 80 years), disease severity (patients with severe ARI), and risk status (those at high risk for severe disease due to underlying comorbidities).

TAKEAWAY:

• Overall, 0.3% of case patients, 3.6% of strict control individuals, and 3.4% of broad control individuals received the RSVpreF vaccine.
• Adjusted VE against ED visits or hospitalizations for RSV-related ARI was 92% (95% CI, 64%-98%) when compared with strict control individuals and 90% (95% CI, 62%–98%) when compared with broad control individuals.
• VE was 95% among older patients (≥ 75 years or ≥ 80 years) and 92% among those with high‑risk chronic medical conditions.

IN PRACTICE:

“Given the introduction of new preventive measures to protect against disease and death due to RSV, expansion of RSV testing is warranted, particularly in high-acuity settings — to better characterize populations at highest risk for RSV infection and potentially to improve treatment algorithms,” the authors wrote.

SOURCE:

This study was led by Sara Y. Tartof, PhD, Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, California. It was published online on October 21, 2025, in Clinical Infectious Diseases.

LIMITATIONS:

A shorter follow-up period after vaccination compared with that in other real-world studies may have contributed to higher VE estimates. Although both RSVpreF and RSVpreF3 were licensed for older adults at the time of this study, the analysis evaluated only RSVpreF. Additionally, low RSVpreF uptake in the first season after licensure but before routine recommendation limited the ability to conduct additional subgroup analyses, particularly among immunocompromised and frail populations.

DISCLOSURES:

This study received funding from Pfizer Inc, with financial support provided directly to the institution. Several authors declared being employees of or holding stock and/or stock options in Pfizer, whereas several others declared being KPSC employees. Few authors received research support or honoraria from various pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.