Impact of maternal RSV vaccine on bronchiolitis healthcare activity in infants in Northwest London

Background

In England, maternal respiratory syncytial virus (RSV) vaccination was introduced for women of 28 weeks’ gestation onwards from 1 September 2024. We aimed to evaluate the impact of population-level maternal RSV prophylaxis on General Practitioner (GP) contacts and hospital admissions for bronchiolitis among infants aged <1 year in Northwest London.

Methods

We used the Northwest London Discover-NOW routinely collected, de-identified dataset to identify infants aged <1 year with GP contacts or hospital admissions for bronchiolitis from September 2018 to February 2026. We applied quasipoisson interrupted time series analyses, adjusting for seasonality and the covid period, using an intervention date of 1 September 2024.

Results

A total number of 199,921 infants were born during the period and included in the study. There were 12,481 GP contacts and 5,319 hospital admissions for bronchiolitis over the study period. There was a + 0.2% (95 CI -5.8%, +6.2%) change in GP contacts in the first post-vaccination implementation season (October 2024- March 2025) and there was a -24.1% (95% CI -30.1%, -18.0%) change in GP contacts in the second post-vaccination implementation season (October 2025- March 2026). There was a -1.2% (95 CI -6.6%, +4.2%) change in hospital admissions in the first season and there was a -18.9% (95 CI -24.4%, -13.3%) change in hospital admissions in the second season.

Conclusions

Initial findings suggest no impact of the maternal RSV vaccine on GP contacts and hospital admissions for bronchiolitis among infants aged <1 year in the first season, but significant impact in the most recent season. These early findings suggest that there could be significant public health and health service benefit from the maternal RSV vaccine. Future research should examine the impact of the maternal RSV vaccine amongst socioeconomic groups to inform policy and ensure equitable population benefits.

Key messages

• The maternal RSV vaccine may have reduced primary and secondary healthcare contacts for bronchiolitis for infants under one year of age.

• The long-term impact of the introduction of the maternal RSV vaccine requires monitoring to ensure equitable access and may impact health service planning.