Influenza Vaccine Review Supports Effectiveness With No New Safety Concerns

A systematic review published in JAMA found that evidence released since August 2025 continued to associate seasonal influenza vaccination with lower risks of serious illness, hospitalization, and influenza-related death across several populations. The review did not identify new safety concerns.

Investigators searched Medline, Embase, Cochrane CENTRAL, and Scopus from August 1, 2025, through June 30, 2026, for English-language, peer-reviewed studies of influenza epidemiology in the US or the effectiveness and safety of US-licensed seasonal influenza vaccines. The review included 69 publications: 21 randomized clinical trials, 23 comparative observational studies, 7 noncomparative product-safety studies, and 18 descriptive studies. The underlying data spanned influenza seasons from 2015 through 2026, and the investigators assessed risk of bias.

For the 2025-2026 season, estimated vaccine effectiveness against influenza-related hospitalization was 31.0% (95% CI, 21.0%-39.0%) among adults aged 65 years or older and 29.0% (95% CI, 11.0%-45.0%) among adults aged 18 to 64 years. Across studies of the 2024-2025 season, effectiveness against influenza-related mortality among older adults ranged from 29.0% to 65.8%.

Vaccination during pregnancy was associated with 44.4% effectiveness against laboratory-confirmed influenza among 245,498 infants during their first 6 months of life. An 8-season case-cohort analysis of 1,086 individuals aged 6 months to 17 years estimated 80.0% effectiveness against influenza-related mortality. In the 332,438-participant DANFLU-2 trial, high-dose vaccination had 43.6% relative effectiveness against influenza-related hospitalization compared with standard-dose vaccination over 3 seasons.

The authors noted that relatively few included studies had a low risk of bias; some lacked an appropriate comparator or adequate power to detect rare events. Generalizability was also limited for some populations and settings, and the narrow search window meant the review was not comprehensive for every season or vaccine product.

Source: Senerth E, Sheikholeslamian SM, Sivakumaran K, et al. Influenza vaccine effectiveness and safety for the 2026-2027 respiratory season. JAMA. Published online September 2, 2026. doi:10.1001/jama.2026.18126