April 21, 2026

expert reaction sequential safety surveillance of RSVpreF vaccination during pregnancy early in the post approval period

A surveillance study published in JAMA Network Open looks at the RSVpreF vaccine during pregnancy.

Prof Adam Finn, Professor of Paediatrics, University of Bristol, said:

“The most recent data on the UK maternal vaccination programme which protects babies against severe lung and breathing problems in their first winter season by vaccinating their mothers against the virus RSV have just been published (1) and confirm that approach is highly effective. This new JAMA network open paper (just press released) focuses on the safety of the vaccine and in particular seems to reconfirm that the vaccine does not increase the risk of premature delivery – which had been raised as a possibility in earlier studies. The researchers also looked at several other problems that can occasionally occur in pregnancy and found slightly higher rates in vaccinated mothers for some and lower rates for others – for example problems with high blood pressure or early breaking of the waters were seen slightly more frequently. These observations don’t prove that the vaccine is causing any such problems – associations like this can occur by chance or because of different kinds of bias and therefore don’t necessarily mean that one thing is the cause of the other – and indeed it’s hard to imagine how it possibly could in some cases – they simply raise questions that will need to be addressed and ultimately settled in future studies. Accordingly, we can conclude, based on the most recent scientific evidence, that the RSV vaccine in pregnancy is very effective at preventing a common serious wintertime illness in babies and that studies to monitor and confirm the safety of this and other vaccines must continue. 

Also of note, the same group have recently published an analysis of their data which showed no statistically significant increases in preterm birth, hypertensive disorders of pregnancy (high blood pressure), premature rupture of membranes (PROM) (early breaking of the waters), or preterm PROM. This analysis may be the one referred to in this new paper as forthcoming. (2)

1 –  (BMJ 2026;393:s752 http://doi.org/10.1136/bmj.s752)  

2 – (JAMA Published Online: January 8, 2026, 2026;335;(5):456-459. doi:10.1001/jama.2025.23452)

Prof Simon Drysdale, Associate Professor and Consultant in Paediatric Infectious Diseases and Immunology at the Oxford Vaccine Group, University of Oxford and Oxford Children’s Hospital, said:

“This study used several large healthcare databases in the US to investigate associations between the maternal RSV vaccine and safety findings. 

“Utilising large databases like in this study is a useful way of pulling together and analysing large volumes of patient data, but it can also have various biases and confounders which may impact the results, as the authors of the article acknowledge. 

“The study cannot confirm a causal association between receipt of the vaccine and the findings, but demonstrates associations that warrant further investigation. Nevertheless, the study reports some interesting findings. 

“These early US data are reassuring in showing no increase in preterm delivery in pregnant individuals vaccinated with the RSV vaccine. 

“However, in this study, vaccination was given at 32–36 weeks’ gestation, which differs from the broader window used in the current UK programme (28 weeks’ gestation up until delivery). 

“Just over half of those vaccinated were already at a higher risk of preterm delivery, which is important when interpreting the findings. 

“There was no signal for Guillain–Barré syndrome, a rare adverse event that has been reported in small numbers of vaccinated older adults. 

“As seen in previous studies, there were higher rates of high blood pressure problems during pregnancy and early breaking of the waters (premature rupture of membranes), but these were not associated with an overall increase in preterm birth in this study.

“Overall, this study highlights that the maternal RSV vaccine is very safe when used in a routine vaccine programme and that there should be ongoing efforts to encourage pregnant individuals to receive this vaccine when they are offered it.”

‘Sequential Safety Surveillance of RSVpreF Vaccination During Pregnancy Early in the Postapproval Period’ by Ashley I. Michnick et al. was published in JAMA Network open 16:00 UK Time Tuesday 21st of April 2026. 

DOI: 10.1001/jamanetworkopen.2026.6190

Declared interests

Prof Adam Finn: “AF previously led research on vaccine preventable diseases including RSV in older adults which was funded by Pfizer who manufacture the RSV vaccine currently used in the UK in pregnancy“

Prof Simon Drysdale: “SD has previously received honoraria from Sanofi for taking part in RSV advisory boards and has provided consultancy and/or investigator roles in relation to product development for Janssen, AstraZeneca, Pfizer, Moderna, Valneva, MSD, iLiAD, MundiPharma and Sanofi with fees paid to my institution. SD is a member of the UK Department of Health and Social Care’s (DHSC) Joint Committee on Vaccination and Immunisation (JCVI) RSV subcommittee and Medicines and Healthcare products Regulatory Agency’s (MHRA) Paediatric Medicine Expert Advisory Group (PMEAG), but the reviews expressed herein do not necessarily represent those of DHSC, JCVI, MHRA or PMEAG.”