A large real-world study from the UK Health Security Agency presented at ESCMID Global 2026 finds that maternal RSV vaccination given at least two weeks before birth cuts infant hospitalizations by more than 80%.
A major new real-world study has found that maternal vaccination against respiratory syncytial virus (RSV) can dramatically reduce the risk of severe illness in infants, cutting hospitalizations by more than 80% when administered at least two weeks before birth.
Presented at ESCMID Global 2026 in Munich, the research—conducted by the UK Health Security Agency—analyzed data from nearly 290,000 infants born in England between September 2024 and March 2025. The findings represent the largest real-world evaluation of maternal RSV vaccination to date.
RSV is a leading cause of infant hospitalizations worldwide, often resulting in serious lower respiratory tract infections such as bronchiolitis and pneumonia. Despite being common, RSV can have lasting health impacts, including recurrent wheezing and impaired lung function.
The study found that although infants born to unvaccinated mothers made up just over half of the population, they accounted for more than 87% of RSV-related hospitalizations. In contrast, infants whose mothers received the vaccine at least 14 days before delivery experienced significantly lower hospitalization rates, with vaccine effectiveness estimated at 81.3%.
“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,” said lead author Matt Wilson, MD, emphasized the importance of timing in achieving optimal protection.
Maternal RSV vaccination reduced infant hospitalizations by over 80%, with unvaccinated mothers’ infants accounting for the vast majority (87%) of severe cases.
Protection increases the earlier the vaccine is given before birth, reaching up to ~85% effectiveness when administered at least four weeks prior to delivery.
The vaccine also significantly protects vulnerable groups like preterm infants, supporting wider adoption of maternal RSV immunization programs globally.
“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 benefits extended to vulnerable populations as well. Among preterm infants—who are at higher risk of severe RSV infection—vaccine effectiveness reached nearly 70% when administered at least two weeks before birth.
The findings support current recommendations to vaccinate during the early third trimester and suggest that broader adoption of maternal RSV immunization programs could significantly reduce infant morbidity worldwide, particularly in regions where RSV remains a leading cause of infant mortality.
The findings were presented at the ongoing ESCMID Global conference.
