Respiratory Virus Vaccine Reduced Number of Babies Hospitalized by 72%

Researchers found the respiratory syncytial virus (RSV) vaccine, introduced across the UK in late summer 2024, led to a 72 per cent reduction in babies hospitalised with the virus if mothers were vaccinated.

The findings are the first to show the real-world effectiveness of the vaccine in pregnant women in the UK.

Uptake of the jab among pregnant women could help to limit the number of sick babies each winter, reducing hospital pressures, experts say. 

Virus protection

RSV is a common virus that causes coughs and colds but can lead to a severe lung infection called bronchiolitis, which can be dangerous in babies, with some requiring admission to intensive care. The virus is the main infectious cause of hospitalisation for babies in the UK and globally.

Receiving the vaccine during pregnancy helps to protect both mother and baby. Antibodies – proteins which help to prevent the virus causing severe infection – produced by the mother in response to the vaccine are passed to the fetus, providing protection from severe RSV for the first six months after birth.

Hospital admissions

The research team, led by the Universities of Edinburgh and Leicester, recruited 537 babies across England and Scotland who had been admitted to hospital with severe respiratory disease in the winter of 2024-2025, the first season of vaccine implementation. 391 of the babies tested positive for RSV. 

Mothers of babies who did not have RSV were two times more likely to have received the vaccine before delivery than the mothers of RSV-positive babies – 41 per cent compared with 19 per cent.

Vaccinate early

Receiving the vaccine more than 14 days before delivery offered a higher protective effect, with a 72 per cent reduction in hospital admissions compared with 58 per cent for infants whose mothers were vaccinated at any time before delivery. 

Experts recommend getting vaccinated as soon as possible from 28 weeks of pregnancy to provide the best protection, as this allows more time for the mother to generate and pass on protective antibodies to the baby, but the jab can be given up to birth.

Improve uptake

Previous research has found that only half of expectant mothers in England and Scotland are currently receiving the RSV vaccine, despite its high success at preventing serious illness.

The findings highlight the importance of raising awareness of the availability and effectiveness of the new vaccine to help protect babies, experts say.

Large collaboration

The research collaboration also included the Universities of Bristol, Oxford, Queen’s University Belfast, UCL and Imperial College London and 30 hospitals across England and Scotland.

The study was funded by the Innovative Medicines Initiative (IMI) Respiratory Syncytial Virus Consortium in Europe (RESCEU), Wellcome and National Institute for Health and Care Research (NIHR) Health Protection Research Unit in Respiratory Infections, Imperial College London.

Reference: Williams TC, Marlow R, Cunningham S, et al. Bivalent prefusion F vaccination in pregnancy and respiratory syncytial virus hospitalisation in infants in the UK: results of a multicentre, test-negative, case-control study. Lancet Child Adolesc Health. 2025. doi: 10.1016/S2352-4642(25)00155-5

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