Building on the Evidence to Recommendations frameworks of the 2023-2024 iteration of the Advisory Committee on Immunization Practices, a systematic review and meta-analysis conducted by infectious disease specialists across the US brings forward evidence to inform 2025-2026 vaccination against COVID-19, respiratory syncytial virus (RSV), and influenza.1
"Recent changes to federal vaccine advisory processes have disrupted immunization guidance, which underscores the need for independent evidence assessment," explains lead author Jake Scott, MD, of the Division of Infectious Diseases & Geographic Medicine at Stanford University School of Medicine in California, and colleagues.
The review of evidence on vaccines was supported by the Vaccine Integrity Project, developed by the Center for Infectious Disease Research and Policy (CIDRAP). The project was launched by CIDRAP in April, which was formed in 2001 at the University of Minnesota in Minneapolis. The news release announcing the project indicated that it "will engage professionals across the US immunization landscape to gather feedback on how nongovernmental entities may be able to help protect vaccine policy, information, and utilization across the US."2
What You Need to Know
Evidence from more than 500 studies confirms that COVID-19, RSV, and influenza vaccines provide meaningful protection against hospitalization—often above 45–70% depending on the vaccine and population.
Serious adverse events such as myocarditis or Guillain-Barré syndrome were uncommon, and data showed no increased risks for adverse pregnancy outcomes; several vaccines even showed benefits like reduced preterm birth.
Studies show that giving COVID-19, influenza, and RSV vaccines together yields immunogenicity and safety comparable to spacing them out, supporting streamlined vaccination strategies for the 2025–2026 season.
The review was conducted by academic researchers and clinical experts over a 12-week period. It is intended, they indicate, "to provide clinicians, medical societies, public health professionals, insurers, and policy makers with timely evidence for the 2025-2026 respiratory virus season."
The investigators included randomized controlled trials (RCTs) and observational studies addressing 4 domains: US epidemiologic surveillance, laboratory-confirmed vaccine efficacy or effectiveness, safety, and vaccine coadministration. They culled 511 studies for inclusion from 1406 that underwent full-text review, comprising RCTs (12%), cohort studies (24%), case-control series (16%), and other observational designs (48%).
Efficacy determinations included:
- COVID-19 messenger RNA vaccines against the XBB.1.5 subvariant had pooled vaccine effectiveness against hospitalization of 46% (CI, 34%-55%) from cohort studies and 50% (43%-57%) from case-control studies, with lower protection among immunocompromised adults. Vaccines against the KP.2 subvariant showed 68% (42%-82%) effectiveness in case-control studies.
- Maternal RSV vaccination for infant protection, nirsevimab for infants, and RSV vaccines in adults 60 years or older showed effectiveness of at least 68% against hospitalization.
- Influenza vaccination had pooled vaccine effectiveness of 48% (39%-55%) in adults aged 18 to 64 years and 67% (58%-75%) in children against hospitalization.
