The 2026-27 influenza evidence review: 80% effectiveness against paediatric influenza death, 19-43% against hospitalisation in older adults

Design

systematic review of studies published August 2025 to June 2026, with risk-of-bias assessment

Population

69 studies covering older adults, adults, pregnancy, children and young people, and immunocompromised people in the US

Primary outcome

vaccine effectiveness against influenza outcomes, and vaccine safety

Effect

older adults: VE 19.0-43.0% against hospitalisation and 29.0-65.8% against mortality; ages 6 months to 17 years: VE 80.0% (95% CI 75.0-84.0) against influenza-associated death; high-dose vs standard-dose relative VE against hospitalisation 43.6% (95% CI 27.5-56.3)

The annual systematic review supporting US seasonal vaccine recommendations identified 69 eligible studies published between August 2025 and June 2026 — 21 randomised trials, 23 comparative observational studies, and the rest safety and burden reports.

The effectiveness estimates are worth quoting accurately because they are routinely overstated in both directions. In older adults, effectiveness against influenza-related hospitalisation ranged across seasons from 19.0% to 43.0%, and against mortality from 29.0% to 65.8%. In children and young people aged 6 months to 17 years, a case-cohort analysis across eight seasons put effectiveness against laboratory-confirmed influenza-associated death at 80.0%. Vaccination in pregnancy was associated with 44.4% effectiveness against symptomatic disease in the infant.

Two results bear on conversations clinicians have every week. High-dose vaccine outperformed standard dose against hospitalisation in older adults, with a relative effectiveness of 43.6%. And a self-controlled case series of nearly ten million people found no increase in serious adverse events, including Guillain-Barre syndrome, whether influenza vaccine was given alone or alongside RSV or COVID-19 immunisation — which answers the coadministration question directly.

These are United States data on US-licensed formulations. Indian influenza seasonality is not the northern-hemisphere autumn pattern these campaigns are built around, so the timing does not transfer even where the effectiveness estimates broadly do.

• Quote modest, honest numbers for older adults — protection against hospitalisation, not against catching influenza
• Offer high-dose formulation to older adults where it is available; relative effectiveness against hospitalisation was 43.6%
• Coadminister with RSV or COVID-19 vaccine without hesitation on safety grounds
• Vaccinate in pregnancy for the infant's benefit as well as the mother's
• Do not apply northern-hemisphere campaign timing to Indian practice; local seasonality governs when to vaccinate

The statistics, in plain English

The effectiveness figures are presented as ranges across seasons rather than as a single pooled estimate, which is the honest way to report influenza vaccine performance — it varies with how well the strains match each year. The lowest hospitalisation estimate in older adults, 19.0% with a 95% CI of 0.0% to 34.0%, has a lower bound at zero, meaning that particular season's data could not exclude no effect at all. The paediatric mortality figure of 80.0% (95% CI 75.0-84.0) comes from a case-cohort design over eight seasons, which is observational and subject to confounding by who gets vaccinated, though the effect size is large enough that confounding alone is an unlikely explanation.

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