Nirsevimab Reduces Risk of RSV in Babies by 87%
In the largest world study, there was a 98% reduction in hospitalizations of babies who received the RSV vaccine compared with those who did not receive the RSV vaccine.
A new study published yesterday in the journal Pediatrics demonstrated that nirsevimab-alip (Beyfortus) injection was highly efficacious in preventing respiratory syncytial virus (RSV)–associated lower respiratory tract disease (LRTD).1
"These results support Beyfortus as a groundbreaking advancement in infant RSV disease prevention. With more than 40 real-world evidence studies to date, this latest study further strengthens the well-established body of data that shows that Beyfortus provides protection against RSV disease to help safeguard the health of all babies, regardless of whether they are born before or during the RSV season," Ayman Chit, PhD, head of vaccines medical in North America at Sanofi, said in a statement.2
The injection met both of its coprimary end points. The first end point showed babies who were administered nirsevimab were 87% (CI, 81.7%-91.1%; P < .0001) less likely to develop RSV disease compared with babies who did not receive the injection. The second coprimary end point showed that if a baby who received nirsevimab later had positive test results for RSV lung infection, there were fewer overall medical visits (adjusted mean difference, –0.86; P = .001) during the illness, including significantly reduced visits to emergency departments and hospitalizations.1
Study Parameters and Other Takeaways
The study was conducted during the 2023-2024 RSV season, and all nirsevimab-eligible, healthy term infants born in April 2023 or later were included. Infants of RSV-vaccinated mothers or with high-risk conditions were excluded from the study, and it included 31,900 infants; 15,647 (49.1%) received nirsevimab.1
Overall, there were 35 RSV LRTD episodes (6.10 per 1000 person-years) among nirsevimab-immunized infants vs 462 (58.51 per 1000 person-years) among nonimmunized infants.1
Additionally, a post hoc analysis of the study evaluated the effectiveness of nirsevimab in preventing RSV hospitalizations among healthy term babies. Using real-world data from a retrospective cohort design, researchers compared hospitalization rates between babies who received nirsevimab and those who did not. The analysis demonstrated a 98% reduction in RSV hospitalizations among babies given the vaccine compared with those who were not given the vaccine.2
Uptake Challenges
Findings from one study found uptake of the injection was a major challenge, despite favorable findings of protection. Moline et al reported that during that same 2023-2024 RSV season, uptake of the injection remained low, with only 1% of children with RSV and 15% of RSV-negative controls receiving nirsevimab during the study period.3
Results from a survey given to pediatricians and obstetrician-gynecologists showed some of the primary challenges to update included parent concerns around the safety and effectiveness of the products, the financial burden of purchasing the products, and reimbursement issues. The survey was conducted in October 2024 and included 200 pediatricians and 200 ob-gyns.4
The findings showed that 77.0% of pediatricians offered nirsevimab and 63.0% of ob-gyns offered the RSV vaccine to pregnant women. Providers were confident in the safety and effectiveness of nirsevimab and maternal RSV vaccine.4
References
1. Hsiao A, Hansen J, Fireman B, et al. Effectiveness of nirsevimab against RSV and RSV-related events in infants. Pediatrics. 2025;156(2):e2024069510. doi:10.1542/peds.2024-069510
2. BEYFORTUS reduced hospital and doctor visits for RSV disease in babies by 87%, according to largest US real-world study. Sanofi. July 22, 2025. Accessed July 23, 2025.
https://www.prnewswire.com/news-releases/beyfortus-reduced-hospital-and-doctor-visits-for-rsv-disease-in-babies-by-87-according-to-largest-us-real-world-study-302510941.html
3. Moline HL, Toepfer AP, Tannis A, et al. Respiratory syncytial virus disease burden and nirsevimab effectiveness in young children from 2023-2024. JAMA Pediatr. Published online December 9, 2024. doi:10.1001/jamapediatrics.2024.5572
4. Pediatrician and ob/gyn survey on RSV immunization. Centers for Disease Control and Prevention. November 14, 2024. Accessed July 23, 2025.
https://www.cdc.gov/rsvvaxview/publications/rsv-immunization-survey-2024.html
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