What to promise about RSV immunisation this season

Design

systematic evidence review of 75 studies, including 12 randomised trials and 33 comparative observational studies

Population

older adults, adults, immunocompromised people, infants and children, and people vaccinated during pregnancy, in US-licensed programmes

Primary outcome

effectiveness against RSV-related hospitalisation and laboratory-confirmed illness, and adverse events of special interest

Effect

older adults 83.3% (95% CI 42.9 to 96.9); maternal 51.0% to 70.0%; nirsevimab 63.6% to 93.0% against RSV hospitalisation

A JAMA evidence review searched from August 2025 to June 2026 and pulled together 75 studies - 12 randomised trials, 33 comparative observational studies, and the rest single-arm or descriptive - on the US-licensed RSV vaccines and monoclonal antibodies. It is the reference for what to tell a patient asking whether the injection is worth it.

In older adults, vaccination was associated with an 83.3% reduction in RSV-related hospitalisation, though the confidence interval is wide (95% CI 42.9% to 96.9%). Protection looked weaker with time: one study found effectiveness clearly lower at 12 to 18 months than in the first season, while another comparing one season with two did not. Maternal vaccination at 32 to 36 weeks' gestation gave 51.0% (95% CI -29.6% to 83.3%) to 70.0% (37.0% to 86.0%) against infant hospitalisation. Nirsevimab in infants ranged from 63.6% (26.9% to 81.9%) to 93.0% (83.0% to 97.0%), the spread driven by timing relative to the season.

On safety, no Guillain-Barre syndrome occurred across three randomised trials; one self-controlled case series in older adults suggested a possible raised risk in the 42 days after vaccination. No comparative study linked vaccination in pregnancy to preterm birth. All of this describes products licensed and deployed in the US, so what is offerable locally, and when in the season it is offered, decides how much of this effectiveness a given patient actually gets.

• Time the offer to the local season - nirsevimab effectiveness varied more with timing than with anything else.
• Tell older adults that protection is best in the first season and may wane, rather than implying it is permanent.
• Offer maternal vaccination in the 32 to 36 week window; outside it the evidence does not apply.
• Do not let the Guillain-Barre signal go unmentioned in older adults, but give its actual weight: no cases in three randomised trials, one observational series.
• Check what is actually stocked and reimbursed locally before promising a product - these are US licensure data, not a statement about availability elsewhere.

The statistics, in plain English

These are effectiveness ranges across heterogeneous studies, not a pooled estimate, and the widths matter. An interval of 42.9% to 96.9% around an 83.3% point estimate means the true benefit could be half what the headline says. The maternal figure of 51.0% has an interval running from -29.6% to 83.3% - it crosses zero, so that particular estimate does not exclude no benefit at all, and it is the 70.0% estimate with its 37.0% to 86.0% interval that carries the weight. Most of the underlying studies are observational, which means the comparison is between people who chose vaccination and people who did not, with all the differences that implies.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.