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Updated evidence that has undergone external review supports the safety and effectiveness of the coronavirus disease 2019 (COVID-19), respiratory syncytial virus (RSV) and influenza (flu) vaccines for the 2025-26 respiratory virus season, according to an October 2025 report in the New England Journal of Medicine.[1]
Designed to fill the void in reliable evidence created by the recent undermining of federal vaccine-advisory processes, the systematic review from academic researchers was...
Updated evidence that has undergone external review supports the safety and effectiveness of the coronavirus disease 2019 (COVID-19), respiratory syncytial virus (RSV) and influenza (flu) vaccines for the 2025-26 respiratory virus season, according to an October 2025 report in the New England Journal of Medicine.[1]
Designed to fill the void in reliable evidence created by the recent undermining of federal vaccine-advisory processes, the systematic review from academic researchers was conducted with support from the Vaccine Integrity Project of the Center for Infectious Disease Research and Policy at the University of Minnesota and an unrestricted grant from the Alumbra Innovations Foundation.[2]
The systematic review
The authors identified 511 studies (12% were randomized controlled trials, and the remaining 88% were observational studies with various designs), published between mid-2023 (for flu) or mid-2024 (for COVID-19 and RSV) and mid-2025, about the safety and effectiveness of U.S.-licensed vaccines for these respiratory viruses. The authors used the evidence-based review methods that the Advisory Committee on Immunization Practices (ACIP) and the Centers for Disease Control and Prevention (CDC) used to inform the deployment of vaccines during the 2023-24 season.
Pooled effectiveness estimates were calculated if at least three separate studies were available for an analytic group (for example, adults receiving COVID-19 vaccination). Effectiveness against hospitalization was the main efficacy outcome used to assess each vaccine.
For COVID-19 vaccines, trials in adults, older adults and people who were immunocompromised yielded effectiveness estimates against hospitalization of 37% to 56%, calculated across 14 studies. For RSV vaccines in pregnant women, infants and older adults, effectiveness against hospitalizations ranged from 68% to 79%, calculated across 18 studies. For flu vaccines in infants, children, and young and old adults, effectiveness against hospitalization ranged from 42% to 67%, calculated across 40 studies. All these effectiveness estimates were statistically significant.
Safety reviews of birth outcomes across all vaccine types for the three diseases did not show adverse pregnancy outcomes and sometimes were associated with significantly lower rates of adverse outcomes. Pregnancy outcomes assessed were miscarriage, stillbirth, congenital anomalies, preterm birth and gestational hypertension or preeclampsia.
Analyses of safety outcomes unrelated to pregnancy showed only two significant and relatively rare adverse effects. COVID-19 vaccination was associated with an excess of 1.3 to 3.1 myocarditis cases per 100,000 doses given to male adolescents, with a lower risk associated with longer intervals between serial doses. In older adults given the RSV vaccine, there was an excess risk of 1.8 cases of Guillain-Barre syndrome (an autoimmune disease in which the immune system attacks peripheral nerves) per 100,000 doses.
Conclusions
During the 2025-26 respiratory virus season, the systematic review reaffirmed that vaccinations for COVID-19, RSV and flu are likely to be safe and effective for most people, including pregnant women, children and the elderly.
The study authors emphasized that although estimates of about 40% effectiveness against hospitalization “may appear to be modest,” in some groups (such as COVID-19 vaccines in immunocompromised people and flu vaccines in adults) such rates of success still represent “substantial reductions in severe outcomes at the population level.” Thus, much individual suffering is prevented.
With the ACIP and CDC severely disrupted, the findings demonstrate the importance of staying up to date on immunizations for respiratory viruses.
References
[1] Scott J, Abers MS, Marwah HK, et al. Updated evidence for Covid-19, RSV, and influenza vaccines for 2025-2026. N Engl J Med. 2025 Oct 29. https://www.nejm.org/doi/full/10.1056/NEJMsa2514268. Accessed December 1, 2025.
[2] Center for Infectious Disease Research and Policy. Homepage. https://www.cidrap.umn.edu/. Accessed December 1, 2025.
