/PRNewswire/ — Presented today at ESCMID Global 2026, the largest real-world study of its kind shows that maternal respiratory syncytial virus (RSV) vaccination reduces the risk of hospitalization in young infants by more than 80% when administered 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 infant hospitalization worldwide, with early infection linked to potential longer-term effects, including recurrent wheezing or asthma, repeat hospitalizations and worsening lung health.
In England, a national maternal RSV vaccination program was implemented on September 1, 2024, offering the bivalent Prefusion F vaccine to pregnant women from 28 weeks of gestation.
To assess its impact on infant hospitalizations due to RSV-associated LRTI, researchers from the UK Health Security Agency (UKHSA) conducted a retrospective cohort study using national datasets including NHS maternity records, vaccination data, and hospital and laboratory data. The analysis looked at 289,399 infants born between September 2, 2024 and March 24, 2025, around 90% of births in England during this period.
In the entire study population, 4,594 RSV-associated hospitalizations were recorded. Although infants born to unvaccinated mothers represented 55% of the total cohort, they made up 87.2% of hospitalizations.
In contrast, infants whose mothers had been vaccinated at least 14 days before birth had a significantly lower risk of hospitalization, with vaccine effectiveness estimated at 81.3%, compared to the unvaccinated group.
Matt Wilson, lead author of the study and epidemiologist at UKHSA, said: “As this is the largest study to date examining the impact of this vaccine on infant hospitalization, these results provide compelling evidence that vaccination provides substantial protection against serious illness in infants. We found a clear relationship between the timing of vaccination and protection, with effectiveness increasing as the interval between vaccination and delivery lengthens, reaching almost 85% when vaccination occurs at least four weeks before delivery.”
The study also looked at the results obtained in premature babies. The effectiveness of the vaccine was estimated at 69.4% in premature babies, taking into account a delay of at least 14 days between vaccination and birth.
“These findings are particularly important for premature infants, who are among the most vulnerable to serious RSV infections,” Wilson added. “With sufficient time between vaccination and birth, we saw good levels of protection in these babies. »