MUNICH, April 18, 2026 /PRNewswire/ -- The largest real-world study of its kind, presented today at ESCMID Global 2026, shows that maternal vaccination against respiratory syncytial virus (RSV) reduces the risk of hospitalisation in young infants by over 80% when given at least two weeks before birth.

RSV is a common virus that can cause severe respiratory illness in infants and young children, including lower respiratory tract infections (LRTIs) such as bronchiolitis and pneumonia. It is a leading cause of infant hospitalisation worldwide, with early-life infection linked to potential longer-term effects including recurrent wheeze or asthma, repeat hospital admissions and impaired lung health.

In England, a national maternal RSV vaccination programme was introduced on 1 September 2024, offering the Bivalent Prefusion F vaccine to pregnant women from 28 weeks' gestation.

To evaluate its impact on infant hospitalisations due to RSV-associated LRTI, researchers from the UK Health Security Agency (UKHSA) conducted a retrospective cohort study using linked national datasets, including NHS maternity records, immunisation data and hospital and laboratory data. The analysis included 289,399 infants born between 2 September 2024 and 24 March 2025, representing around 90% of births in England during this period.

Across the study population, 4,594 RSV-associated hospitalisations were recorded. Although infants born to unvaccinated mothers made up 55% of the total cohort, they accounted for 87.2% of hospitalisations.

In contrast, infants whose mothers were vaccinated at least 14 days before birth had a markedly lower risk of hospitalisation, with vaccine effectiveness estimated at 81.3%, relative to the unvaccinated group.

Lead author and UKHSA epidemiologist Matt Wilson commented, "As the largest study to date examining the impact of this vaccine on infant hospitalisation, these findings provide robust evidence that vaccination offers substantial protection against severe illness in young infants. We found a clear relationship between timing and protection, with effectiveness increasing as the interval between vaccination and birth lengthens, reaching close to 85% when vaccination occurs at least four weeks before delivery."

The study also investigated outcomes in preterm infants. Vaccine effectiveness was estimated at 69.4% in preterm infants, when allowing at least 14 days between vaccination and birth.  

"These findings are particularly important for preterm infants, who are among the most vulnerable to severe RSV infection," added Wilson. "With sufficient time between vaccination and birth, we saw good levels of protection in these babies."

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