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.