/PRNewswire/ — The largest real-world study of its kind to date, presented today at ESCMID Global 2026, shows that RSV vaccination during pregnancy reduces the risk of hospitalization in young infants by more than 80% when given at least two weeks before birth.
RSV is a common virus that can cause serious respiratory illnesses in infants and young children, including lower respiratory tract infections (LRTIs) such as bronchiolitis and pneumonia. It is a leading cause of hospitalization in infants worldwide, with infection in the first few months of life being linked to potential long-term consequences such as recurrent wheezing or asthma, repeated hospitalizations and impaired lung health.
A national RSV vaccination program for pregnant women was introduced in England on 1 September 2024, offering the bivalent Prefusion-F vaccine to pregnant women from 28 weeks of pregnancy.
To assess the impact of this program on infant hospitalizations for RSV-associated lower respiratory tract infections, researchers at the UK Health Security Agency (UKHSA) conducted a retrospective cohort study using linked national datasets, including NHS pregnancy data, vaccination data, and hospital and laboratory data. The analysis included 289,399 infants born between September 2, 2024 and March 24, 2025, representing around 90% of all births in England during this period.
In the entire study population, 4594 RSV-associated hospitalizations were recorded. Although infants born to unvaccinated mothers comprised 55% of the total cohort, they accounted for 87.2% of hospitalizations.
In contrast, the risk of hospitalization was significantly lower for infants whose mothers had been vaccinated at least 14 days before birth; the effectiveness of the vaccine was estimated at 81.3% compared to the unvaccinated group.
Lead study author and UKHSA epidemiologist Matt Wilson said: “As the largest study to date of the impact of this vaccine on infant hospitalizations, these results provide strong evidence that vaccination provides significant protection against serious disease in young infants. We found a clear association between the timing of vaccination and protection. Effectiveness increased as the interval between vaccination and birth increased, reaching almost 85% when vaccination was given at least four weeks before delivery.”
The study also looked at outcomes in premature babies. The effectiveness of the vaccine was estimated at 69.4% in premature babies when there was at least 14 days between vaccination and birth.
“These findings are particularly important for premature infants, who are among the infants most at risk of severe RSV infections,” Wilson added. “If there was enough time between vaccination and birth, we observed a good protective effect in these babies.”