A real-world study from the UK Health Security Agency shows maternal RSV vaccination provides significant protection for infants when mothers are vaccinated at least two weeks before delivery.


RT’s Three Key Takeaways:

  1. Significant Hospitalization Reduction: Maternal vaccination against respiratory syncytial virus (RSV) reduces the risk of hospitalization in young infants by more than 80% when administered at least 14 days before birth.
  2. Timing of Administration: Vaccine effectiveness increases as the interval between vaccination and delivery lengthens, reaching approximately 85% when given at least 4 weeks before birth.
  3. Protection for Preterm Infants: The study found that the vaccine remains effective for preterm infants, offering nearly 70% protection against severe illness when given at least 14 days before delivery.


Maternal vaccination against respiratory syncytial virus (RSV) reduces the risk of hospitalization in young infants by more than 80% when administered at least 14 days before birth, according to a study from the UK Health Security Agency (UKHSA).

The findings, presented at ESCMID Global 2026, represent the largest real-world study of its kind. 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. Early-life infection is a leading cause of infant hospitalization worldwide and is linked to long-term effects, including recurrent wheeze, asthma, repeat hospital admissions, and impaired lung health.

Researchers from the UKHSA conducted a retrospective cohort study using linked national datasets, including National Health Service (NHS) maternity records, immunization data, and hospital and laboratory records. The analysis included 289,399 infants born in England between September 2, 2024, and March 24, 2025, representing approximately 90% of births during that period.

Impact on Hospitalization Rates

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

In contrast, infants whose mothers were vaccinated at least 14 days before birth had a significantly lower risk of hospitalization. Vaccine effectiveness was estimated at 81.3% relative to the unvaccinated group.

“As the largest study to date examining the impact of this vaccine on infant hospitalization, these findings provide robust evidence that vaccination offers substantial protection against severe illness in young infants,” said Matt Wilson, lead author and UKHSA epidemiologist. “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 4 weeks before delivery.”

Outcomes for Preterm Infants

The study also investigated outcomes for preterm infants, who are among the most vulnerable to severe RSV infection. For this population, vaccine effectiveness was estimated at 69.4% 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,” said Wilson. “With sufficient time between vaccination and birth, we saw good levels of protection in these babies.”

The national maternal RSV vaccination program was introduced in England on September 1, 2024, offering the bivalent prefusion F vaccine to pregnant women starting at 28 weeks’ gestation to improve infant healthcare outcomes and reduce the burden of respiratory disease.

References:

  1. Wilson, M., Whitaker, H., Walker, J., et al. (2026). Maternal RSV vaccination and reduced risk of hospitalisation for babies in England – 2024/45. Oral presentation. ESCMID Global 2026.
  2. Munro, A. P. S., Martinón-Torres, F., Drysdale, S.B. et al. (2023). The disease burden of respiratory syncytial virus in Infants. Current Opinion in Infectious Diseases. 36(5):379-384.
  3. European Lung Foundation (ELF). (n.d.). Acute lower respiratory infections. https://europeanlung.org/en/information-hub/lung-conditions/acute-lower-respiratory-infections/
  4. World Health Organization. (n.d.). Global Influenza Programme: Respiratory Syncytial Virus Surveillance. https://www.who.int/teams/global-influenza-programme/global-respiratory-syncytial-virus-surveillance
  5. World Health Organization. (2025). WHO outlines recommendations to protect infants against RSV – respiratory syncytial virus. https://www.who.int/news/item/30-05-2025-who-outlines-recommendations-to-protect-infants-against-rsv-respiratory-syncytial-virus
  6. World Health Organization. (2025). Respiratory syncytial virus (RSV). https://www.who.int/news-room/fact-sheets/detail/respiratory-syncytial-virus-(rsv)#:~:text=Respiratory%20syncytial%20virus%20(RSV)%20is,access%20to%20supportive%20medical%20care.