The influenza numbers to quote this season

Design

systematic evidence review of 69 studies, including 21 randomised trials and 23 comparative observational studies

Population

older adults, adults, pregnant people, infants and children, and immunocompromised people, in US-licensed influenza vaccine programmes

Primary outcome

vaccine effectiveness against influenza-related hospitalisation, mortality and severe disease, and adverse events

Effect

older adults hospitalisation 19.0% to 43.0%, mortality 29.0% to 65.8%; children aged 6 months to 17 years 80.0% (95% CI 75.0 to 84.0) against influenza-associated death

A systematic review searching August 2025 to June 2026 identified 69 studies - 21 randomised trials, 23 comparative observational studies, and the rest safety or burden work - on US-licensed seasonal influenza vaccines. It is the reference for what to promise, and where the promise is weaker than people assume.

In older adults, effectiveness against influenza-related hospitalisation ranged across seasons from 19.0% (95% CI 0.0% to 34.0%) to 43.0% (30.0% to 53.0%), and against mortality from 29.0% (16.0% to 40.0%) to 65.8% (54.6% to 76.9%). The strongest single figure is in children: across eight seasons of national surveillance in those aged 6 months to 17 years, effectiveness against laboratory-confirmed influenza-associated death was 80.0% (75.0% to 84.0%). Vaccination in pregnancy gave 44.4% (31.4% to 54.9%) against symptomatic disease in the infant. Randomised data covering 2022 to 2025 favoured high-dose over standard-dose vaccine in older adults, relative effectiveness against hospitalisation 43.6% (27.5% to 56.3%).

On safety, a self-controlled case series in 9973703 vaccinated people found no association with serious adverse events including Guillain-Barre syndrome, whether the influenza vaccine was given alone or alongside RSV or COVID-19 immunisation. Another found no excess of febrile seizure in the 0 to 7 days after vaccination. Coadministration is the practical message: there is no safety reason to split the visits, and a second visit is a visit many patients do not make.

• Offer influenza, COVID-19 and RSV immunisation in the same visit - the coadministration safety data now cover nearly ten million people.
• Use the paediatric figure when parents hesitate: 80% against influenza-associated death, not 80% against catching it.
• Be honest with older adults that hospitalisation effectiveness varies season to season, and the lower estimates touch zero.
• Prefer high-dose formulation in older adults where it is available - the randomised comparison favours it.
• In India seasonal influenza vaccine sits outside the national programme and is bought privately, so the conversation is about cost as well as benefit.

The statistics, in plain English

These are ranges across seasons and study designs, not pooled estimates, and the spread is real rather than statistical noise - influenza vaccine effectiveness genuinely varies with how well the strains match. The lowest hospitalisation estimate, 19.0% with an interval of 0.0% to 34.0%, touches zero, which means that particular season's data could not rule out no benefit at all. Most of these are observational comparisons, so people who accept vaccination differ from those who do not in ways that adjustment only partly handles - the paediatric mortality figure comes from a case-cohort analysis, which is a stronger design than a simple cohort but still not randomised.

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