Real-World Evidence Shows 82% Reduction in Infant RSV Hospitalizations With Nirsevimab


The results reinforce other real-world evidence from several broad infant immunization programs in the US, Spain, and France.

New real-world evidence published in The Lancet shows nirsevimab (Beyfortus; Sanofi and AstraZeneca) resuted in an 82% reduction in infant hospitalizations due to respiratory syncytial virus (RSV) during the 2023-2024 season, compared with no intervention.1

These results are part of the 3-year NIRSE-GAL study conducted in Galicia, Spain, and are from the first RSV season after the introduction of nirsevimab. The results reinforce other real-world evidence from several broad infant immunization programs in the US, Spain, and France during the 2023-2024 RSV season.1

little baby boy is is treated respiratory problem with vapor nebulizer and sister's hand is touching his head to make him feel better, concept of pediatric patient care for sick in the hospital

Image credit: Sukjai Photo |

“Galicia provides the first population-based real-world evidence of the impact of nirsevimab to prevent RSV disease in infants, showing a reduction by almost 90% in the number of hospitalizations due to this virus when compared with several previous RSV seasons,” said Federico Martinon Torres, principal investigator of the NIRSE-GAL study and head of pediatrics at Hospital Clínico Universitario Santiago in Spain, in a news release. “This achievement is the result of the exemplary pragmatic collaboration among scientists, industry, health care providers, and policymakers aligned with a carefully planned rollout of the immunization campaign, and the outstanding response of the Galician parents to this prophylaxis campaign.”1

Nirsevimab is the first immunization designed for all infants to protect against RSV through their first RSV season, including infants born healthy at term or preterm, or those with specific conditions that make them more vulnerable to RSV. It is also designed to protect children up to 2 years of age who remain vulnerable to severe RSV disease through their second RSV season. Nirsevimab is a long-acting antibody administered as a single dose.1

The body of evidence supporting nirsevimab has been rapidly growing. For instance, an interim analysis of 2023-2024 surveillance data published by the CDC showed that a single dose of nirsevimab was 90% effective in preventing RSV-related hospitalizations in infants who were immunized before 8 months of age.2 The report, which evaluated infants who were hospitalized with acute respiratory illness (ARI), found that receipt of nirsevimab was more frequent among infants with high-risk medical conditions compared with those without these conditions (46% vs 6%). Furthermore, time since receipt of nirsevimab to ARI symptom onset ranged from 7 to 127 days, with a median of 45 days.2

In August of 2023, the CDC’s Advisory Committee on Immunization Practices recommended the routine use of nirsevimab for the prevention of RSV lower respiratory tract disease in newborns and infants younger than 8 months during or entering their first RSV season, as well as children aged 8 to 19 months who have an increased risk of contracting RSV and who are entering their second RSV season. Clinical trials supporting its FDA approval demonstrated that a single dose delivered high, consistent, and sustained efficacy against RSV lower respiratory tract disease for up to 5 months, which is the duration of a typical RSV season.3

However, shortages and lack of access have made the rollout of nirsevimab a challenge. In October 2023, the CDC issued a set of recommendations to address a limited supply, which Sanofi said was caused by unprecedented demand during the 2023-2024 season. The CDC recommended that nirsevimab 100 mg doses be prioritized for young infants aged <6 months and those with underlying conditions. Their recommendation for the 50 mg doses were not changed.4

The CDC advises against the use of 2 50-mg doses in infants weighing ≥11 Ibs to maintain the supply of 50 mg doses for infants weighing <11 Ibs. The agency also urged providers to half the use of nirsevimab in children aged 8 to 19 months who are eligible for palivizumab (Synagis; Sobi).4

“The scale and speed of impact seen after Beyfortus’ introduction demonstrates the strength of all-infant immunization strategies against RSV in babies,” said Thomas Triomphe, executive vice president of vaccines at Sanofi, in the news release. “In Galicia, we saw an effectiveness of 82% in reducing RSV hospitalizations following the launch of Beyfortus, with more than 90% of eligible infants immunized. A growing body of evidence from these programs support policymakers, health care providers, and parents who share our collective ambition to safeguard babies from RSV disease.”1

1. Press Release: Beyfortus real-world evidence published in The Lancet shows 82% reduction in infant RSV hospitalizations. News release. Sanofi. May 2, 2024. Accessed May 2, 2024.
2. Moline HL, Tannis A, Toepfer AP, Williams JV, et al. Early estimate of nirsevimab effectiveness for prevention of respiratory syncytial virus-associated hospitalization among infants entering their first respiratory syncytial virus season — new Vaccine Surveillance Network, October 2023-February 2024. MMWR. 2024;73(9):209-214.
3. McGovern G. CDC Recommends Beyfortus for Routine Use to Protect Infants, Young Children Against Respiratory Syncytial Virus. Pharmacy Times. August 29, 2023. Accessed May 2, 2024.
4. CDC Issues Alert to Address Shortage of RSV Treatment Nirsevimab. Pharmacy Times. October 24, 2023. Accessed May 2, 2024.
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