RSV Prevention Gains Ground: French Studies Confirm Safety of Vaccines and Antibody Treatments
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New data from France offers reassurance on the safety of recently approved preventative measures against respiratory syncytial virus (RSV), a leading cause of bronchiolitis in infants.
Each fall and winter, bronchiolitis sends thousands of infants to emergency rooms in France, most frequently enough triggered by respiratory syncytial virus (RSV). The arrival of new preventative treatments – vaccines for adults and monoclonal antibodies for babies – has sparked both hope and concern among parents. Now, comprehensive surveys conducted by the National Medicines Safety Agency (ANSM) are providing critical insights into the real-world safety and usage of these new tools.
Monitoring New Preventative Strategies
To closely monitor the impact of these treatments, the ANSM commissioned two major pharmacovigilance surveys in 2024, alongside a dedicated French study focusing on the Abrysvo vaccine in pregnant women. Results, released at the end of November, meticulously examine the treatments’ tolerance and identify potential usage errors. A key takeaway from the initial findings is a warning regarding proper administration protocols.
Two-Pronged Approach to RSV Prevention
Currently, two main categories of preventative treatments are available in France. The first includes vaccines designed for adults – Abrysvo (particularly recommended for pregnant women to protect their newborns), Arexvy, and mResvia. The second is a monoclonal antibody, Beyfortus (nirsevimab), developed by Sanofi and AstraZeneca, specifically for infants under 24 months of age. regional pharmacovigilance centers (CRPVs) initially reported potential adverse effects associated with Beyfortus – including flu-like symptoms, decreased appetite, reduced muscle tone, and a potential risk of stroke in infants – were not substantiated by the new data, although continued monitoring remains essential. To mitigate confusion, the ANSM has created a resource sheet for healthcare professionals and emphasizes the importance of reporting any adverse effects to regional CRPV centers or thru the national reporting portal.
Abrysvo in Pregnancy: A Large-Scale French Study
A large French study, EPI-PHARE, utilizing data from the National Health Data system (SNDS) and published in November 2025 in Obstetrics and Gynecology, assessed the safety of the Abrysvo vaccine when given during pregnancy. Researchers compared nearly 29,000 vaccinated women with approximately 24,900 unvaccinated pregnant women. The study found no meaningful increase in the risk of premature birth, stillbirth, small-for-gestational-age infants, cesarean section, postpartum hemorrhage, preeclampsia, or serious cardiovascular events in mothers.
Though,a slight,non-significant increase in certain risks was observed in a small subgroup of women vaccinated before or at 32 weeks of gestation,representing only 6% of those vaccinated. “These results should be interpreted with caution,” the authors of the EPI-PHARE study cautioned, as relayed by the Vidal medical site. They also noted that the timing of administration was influenced by findings from the phase III MATISSE trial, which had previously observed a non-significant increase in premature births among women vaccinated before the 32nd week of gestation. These findings support the recommendations of the High Authority of Health, which advocates for administering Abrysvo between 32 and 36 weeks of amenorrhea.
Expanding Prevention Options
The landscape of RSV prevention continues to evolve.In September,the European Medicines Agency (EMA) recommended the approval of another monoclonal antibody,Enflonsia (clesrovimab,MSD laboratory),for use in newborns and infants. As bronchiolitis continues to affect many babies in France each autumn and winter, these preventative tools are being integrated alongside existing hygiene measures and treatment protocols. authorities emphasize that,like all medications,vaccines and monoclonal antibodies can cause undesirable effects and will be subject to ongoing,rigorous monitoring throughout future campaigns.
