Maternal RSV vaccination prevents four in five infant hospitalisations in real use

Design

Systematic review and random-effects meta-analysis of non-randomised post-implementation studies

Population

7112 infants across 7 studies (2684 born to vaccinated mothers), Argentina, UK and US, 2024-2025

Primary outcome

RSV-associated lower respiratory tract infection hospitalisation

Effect

Effectiveness 82 per cent (95 per cent CI 81 to 82) birth to 3 months and 78 per cent (70 to 84) birth to 6 months, with maternal vaccination 14 or more days before delivery

The bivalent prefusion F RSV vaccine given in pregnancy worked in its pivotal trial. The question since has been whether it works when given to whole antenatal populations. Seven post-implementation studies covering 7112 infants, of whom 2684 were born to vaccinated mothers, were pooled from data collected between January 2024 and April 2025 in Argentina, the United Kingdom and the United States.

Against RSV-associated lower respiratory tract infection hospitalisation, pooled effectiveness was 82 per cent from birth to 3 months (three studies, 4397 infants, heterogeneity zero) and 78 per cent from birth to 6 months (95 per cent CI 70 to 84; six studies, 3008 infants, I-squared 18.7 per cent), where mothers were vaccinated at least 14 days before delivery. Effectiveness against emergency department visits, intensive care admission and death could not be pooled - too few data.

Every included study was non-randomised, so vaccinated and unvaccinated mothers differ in ways adjustment only partly handles, and the 14-day interval is doing real work: a dose given closer to delivery has not had time to transfer antibody. For Indian practice the actionable part is not availability, which remains a separate question, but the timing rule. Wherever this vaccine is given, the fortnight before delivery is the deadline, not the target, and an antenatal clinic that offers it late offers less than it thinks.

• Give the vaccine at least 14 days before expected delivery; that interval defines the effectiveness figure.
• Record the vaccination date in the mother's notes in a form the neonatal team will see.
• Do not extend the 78 to 82 per cent figure to intensive care admission or death, which could not be pooled.
• Remember these are non-randomised comparisons; the effect is large but the design is observational.
• Where the vaccine is unavailable, the infant monoclonal remains the alternative route to the same protection.

The statistics, in plain English

Vaccine effectiveness here is derived as one minus the pooled odds ratio, which slightly overstates effectiveness when the outcome is common - hospitalisation is not, so the distortion is small. Treat the birth-to-three-months figure with some caution: a 95 per cent interval of 81 to 82 per cent is implausibly tight for a pooled estimate from three observational studies, and the six-month interval of 70 to 84 per cent is the more honest picture of the uncertainty. Heterogeneity was low in both, meaning the studies agreed with each other - which is reassuring about consistency, not about confounding, since all seven share the same observational weakness.

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.