Sanofi’s NIRSE-GAL Study Shows Beyfortus Protect Infants Beyond First RSV Season

New real-world evidence from Spain demonstrates that early prevention with Beyfortus (nirsevimab), Sanofi’s long-acting monoclonal antibody, provides significant and sustained reductions in RSV-related hospitalizations across two consecutive seasons. Published in The Lancet Infectious Diseases, the NIRSE-GAL study (NCT06180993), the first prospective, population-level evaluation of Beyfortus over multiple seasons underscores the therapy’s potential to transform infant RSV protection and reduce healthcare burdens.

Conducted in Galicia, the study evaluated a universal immunization program with 94.4% coverage among 11,796 eligible infants. Results highlight Beyfortus’ immediate and lasting impact:

• 85.9% reduction (95% CI: 80.2–90.0) in RSV-related lower respiratory tract infection (LRTI) hospitalizations in the first season.
• 55.3% reduction (95% CI: 22.5–74.3) in RSV hospitalizations persisting into the second season among first-season immunized infants.
• 78.2% decline in RSV-related rehospitalizations and 62.4% decline in LRTI-related rehospitalizations in the second season.
• 30.8% reduction in first consultations for acute bronchitis/bronchiolitis; 33.4% reduction consultations for LRTIs; and 27.7% reduction in consultations for wheezing/asthma during the first season.

Building on efficacy and safety from clinical trials, Beyfortus’ real-world effectiveness has been confirmed in over 50 studies involving more than 400,000 immunized infants. Since launch, over 11 million infants across more than 45 countries have received Beyfortus, reinforcing its role in global RSV prevention.

“These findings mark a pivotal advancement in RSV prevention, showing that Beyfortus not only prevents severe disease in the first season but also offers meaningful protection into the second potentially by safeguarding early lung development,” said Federico Martinón-Torres, MD, PhD, principal investigator and head of the Translational Research Network in Pediatrics at Hospital Clínico Universitario de Santiago de Compostela. “This population-level data will inform immunization strategies and economic models worldwide.”

Sanofi echoes this enthusiasm: “The NIRSE-GAL study adds robust, cross-season real-world evidence to the growing body of data supporting Beyfortus’ public health value,” said Thomas Triomphe, Executive Vice President, Vaccines, Sanofi. “As RSV continues to hospitalize infants globally, these results reinforce our commitment to broad, effective prevention that eases the burden on families and healthcare systems.”

RSV remains a leading cause of infant hospitalization worldwide, with most severe cases in healthy, term infants. Nearly all children are infected by age two, driving substantial clinical and economic costs. Beyfortus addresses this gap with a single-dose administration providing rapid, season-long protection without relying on active immunity.

About Beyfortus (Nirsevimab)

Beyfortus is a respiratory syncytial virus (RSV) investigational long-acting monoclonal antibody. Approved for infants born during or entering their first RSV season, and for select children up to 24 months, it offers passive immunity against RSV LRTI. For full Prescribing Information, visit www.beyfortus.com.

Reference

Press Release: Beyfortus study published in The Lancet Infectious Diseases shows benefit for infants beyond first RSV season, 16 February 2026, Press Release: Beyfortus study published in The Lancet Infectious Diseases shows benefit for infants beyond first RSV season

Mallah, NarmeenMallah, Narmeen et al., Full 2023–24 season results of universal prophylaxis with nirsevimab in Galicia, Spain: the NIRSE-GAL study, The Lancet Infectious Diseases, Volume 25, Issue 2, e62 – e63, https://doi.org/10.1016/S1473-3099(24)00811-9

Evaluation of the Effectiveness and Impact of Nirsevimab Administered as Routine Immunization (NIRSE-GAL), ClinicalTrials.gov ID NCT06180993, https://clinicaltrials.gov/study/NCT06180993