Nirsevimab Outperforms Maternal RSV Vaccine in Preventing Infant Hospitalizations

A retrospective cohort study published in The Lancet Child & Adolescent Health found that nirsevimab immunization at birth is associated with a 22% lower risk for respiratory syncytial virus (RSV)-related lower respiratory tract infection (LRTI) hospitalization in infants during their first 6 months of life compared to maternal RSV prefusion F (RSVpreF) vaccination during pregnancy. The analysis of French health data included infants born between September 2024 and February 2025 who either received nirsevimab shortly after delivery or were born to mothers vaccinated with RSVpreF between 28 and 36 weeks of gestation.

The study utilized data from the French National Health Data System, analyzing 164,140 infants in the final analysis. After matching 42,098 infants from each treatment group based on sex, birth date, and region of birth, researchers observed 753 total RSV-related LRTI hospitalizations during the 6-month follow-up period. There were 350 hospitalizations among infants who received nirsevimab (0.83% rate) and 403 among infants exposed to maternal RSVpreF vaccination (0.96% rate). After adjustment for baseline characteristics, nirsevimab demonstrated a significantly lower risk for hospitalization with an odds ratio of 0.78 (95% CI, 0.70-0.86). The difference in effectiveness became apparent after the second month of life and stabilized after the third month.

Additional subgroup analyses showed nirsevimab was associated with lower odds of RSV-related hospitalizations requiring pediatric intensive care admission (OR, 0.41; 95% CI, 0.28-0.61) and invasive or noninvasive ventilation (OR, 0.53; 95% CI, 0.44-0.65). The effectiveness of maternal vaccination varied by timing: when maternal vaccination occurred less than 8 weeks before delivery, nirsevimab remained superior, but when maternal vaccination occurred at least 8 weeks before delivery, no significant difference was observed between the strategies (OR, 1.01; 95% CI, 0.77-1.32).

Meanwhile, a separate UK study analyzing nearly 300,000 babies born between September 2024 and March 2025 found that the maternal RSV vaccine reduces baby hospital admissions for RSV by more than 80% when given at least four weeks before birth. The study followed approximately 90% of all births in England during that period, with over 4,500 babies admitted to hospital—vast majority of whose mothers had not been vaccinated. Current UK guidelines recommend the maternal RSV vaccine, Abrysvo, for pregnant women from 28 weeks of gestation, with protection starting from the day babies are born.

RSV is a leading cause of lower respiratory infections in infants, with severe cases leading to hospitalization. Babies under 1 year old, especially those under 6 months, are most vulnerable. While maternal vaccination remains a primary prevention strategy, nirsevimab—a long-acting monoclonal antibody—offers an alternative protection for infants, particularly those born outside the vaccine window or when maternal vaccination timing is suboptimal. Both strategies aim to protect infants during their most vulnerable first months of life when RSV poses the greatest risk.