Large-scale UKHSA study reveals extraordinary impact of vaccination of mothers in protecting premature infants from chest infections.
A pioneering study has found that the first year of RSV vaccine rollout (2024-25) led to a more than 80% reduction in infants being hospitalised with RSV chest infections.
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It found that vaccination at least two weeks before birth gave 81.3% protection. A narrow range of statistical uncertainty, from 78.9% to 83.4%, means there is high confidence in the vaccine’s protective effect.
The full study, “Maternal RSV vaccination and reduced risk of hospitalisation for babies in England 2024/25”, has just been published in the British Medical Journal. Research was conducted by the UK Health Security Agency (UKHSA). It is thought to be the largest study in the world evaluating the effect of maternal RSV vaccination in preventing infants being hospitalised for chest infection. RSV causes bronchiolitis, an infection and inflammation of the small airways of the lung, and is a major cause of hospital admission in infants.
To protect newborns, the vaccination is now offered to expectant mothers from 28 weeks of pregnancy. The study examined data on nearly 300,000 babies born between September 2024 and March 2025, comprising some 90% of all births in England during that period. Using routinely collected electronic health records, UKHSA researchers assessed the vaccine’s effectiveness in preventing hospital admissions. Of the more than 4,500 hospitalisations that occurred among this cohort, the vast majority had not been vaccinated.
What’s more, the study found that getting the vaccine in week 28 or soon after was the most effective: babies born at least four weeks after their mother was vaccinated had nearly 85% protection. Yet even being vaccinated later in pregnancy had an evident effect. Where vaccination was administered 10 to 13 days before birth, hospital admissions were reduced by 50%.
The researchers conclude that premature babies, who are particularly vulnerable to RSV, can be well protected, provided there is at least two weeks between vaccination and birth.
Uptake of maternal RSV vaccine has been rising steadily in England. It was 55% during the study period, and had risen to 64.1% by November 2025
Matt Wilson, an epidemiologist at UKHSA and lead author of the study, says: ‘Our evaluation of the first season of the programme in England gives important confirmation that maternal RSV vaccination is highly protective for newborn infants, over 80%, and that effectiveness reached nearly 85% when vaccination occurred at least 4 weeks before birth.
‘These findings are also particularly important for preterm infants, who are among the most vulnerable to severe RSV infection. With sufficient time between vaccination and birth, we saw good levels of protection in these babies. Giving the vaccination early in the third trimester, as recommended by the World Health Organization, could protect most preterm infants, so it’s important that midwives and other healthcare workers offer vaccination on time with the schedule – and that pregnant women promptly take it up.’
Dr Conall Watson, Consultant Epidemiologist at UKHSA and one of the senior authors, adds: ‘RSV can cause life-threatening chest infections for babies. Half of newborns will have caught RSV before they are a year old. As an expectant parent you have no idea if they are going to be severely ill or not. Our analysis of the RSV vaccination programme in England is important confirmation of the results from the clinical trial, but this study is 40 times bigger and clearly shows the hugely beneficial effect on reducing hospital admission. Getting vaccinated in week 28 of pregnancy or soon after gives excellent protection to both term and preterm babies when they are tiny and most vulnerable to severe RSV. The RSV vaccine gives a brilliant boost to the pregnant woman’s immune system so it can pass antibodies through the placenta and protect the baby from the day they are born.’
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