Peer-reviewed article
Changes in RSV-associated lower respiratory tract infections among hospitalized and outpatient children under 2 years in Northern Bavaria after general recommendation of Nirsevimab immunization in 2024.
Ying Zhou, Katharina Hecker, Géraldine Engels, Oliver Andres, Kerstin Knies et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study evaluated the impact of Nirsevimab immunization on respiratory syncytial virus (RSV) infections in children under 2 years in Northern Bavaria, Germany. After Nirsevimab was recommended for all newborns in 2024, the proportion of hospitalized infants under 1 year with RSV-associated lower respiratory infections fell significantly from 78-80% to 42%. Similar reductions were observed in outpatient settings and in nationwide laboratory surveillance data, suggesting the immunization effectively reduced severe RSV disease in the youngest children.
Key points
- Nirsevimab immunization coverage for newborns reached 68% (566 of 833) at the study hospital between November 2024 and March 2025
- The proportion of hospitalized children under 1 year with RSV-LRTI decreased from 78-80% in previous seasons to 42% in the 2024-25 season (p < 0.001)
- Nationwide laboratory surveillance showed the proportion of RSV cases in children under 1 year decreased from 65% to 47% between the 2023-24 and 2024-25 RSV seasons
- Outpatient RSV-LRTI cases showed a smaller but still significant decrease in the proportion affecting children under 1 year (60% to 33%, p = 0.014)
- Total hospitalized RSV-LRTI cases among children under 2 years fell from 98 cases to 29 cases across the three seasons studied
Limitations
This is a single-center study with observational design and no randomization, making it difficult to definitively attribute changes solely to Nirsevimab rather than other factors such as seasonal variation or behavioral changes. The study cannot determine individual-level protection or identify which children received Nirsevimab versus those who did not.
Abstract
PURPOSE: This study investigated changes in the incidence and age distribution of RSV-associated lower respiratory tract infections (RSV-LRTI) among children in Northern Bavaria after the general recommendation of Nirsevimab immunization in 2024. METHODS: Postnatal Nirsevimab immunization coverage was assessed at the University Hospital Würzburg (UKW) in children born between 11/2024 and 03/2025. Age distribution of in- and outpatients < 2 years with PCR-confirmed RSV-LRTI was assessed from UKW (ICD-10 based) and pediatric practices in Würzburg for November-March in 2022/23 (S1), 2023/24 (S2) and 2024/25 (S3). Age distribution of RSV cases from nationwide mandatory laboratory RSV surveillance (Robert Koch-Institute) was analyzed for November-March in 2023/24 and 2024/25. RESULTS: Between 11/2024 and 03/2025, postnatal Nirsevimab immunization coverage for newborns at the UKW was 68% (566/833). In the RSV seasons S1/S2/S3, 98/84/29 children < 2 years with RSV-LRTI were hospitalized. The proportion of children < 1 year decreased from 78%/80% in S1/S2 to 42% in S3 (S1 vs. S3 p < 0.001, S2 vs. S3 p < 0.001). In 36/68/30 outpatients < 2 years with RSV-LRTI, the proportion of children < 1 year decreased from 44%/60% in S1/S2 to 33% in S3 (S1 vs. S3 p = 0.358; S2 vs. S3 p = 0.014). In nationwide laboratory RSV surveillance, 23,171/12,826 children < 2 years were reported in S2/S3, with a decrease in the proportion of children < 1 year from 65% in S2 to 47% in S3 (p < 0.001). CONCLUSIONS: We observed a clear decrease of RSV-LRTI in hospitalized and outpatient infants < 1 year of age in the first RSV season, suggesting a relevant impact following Nirsevimab recommendation in Germany.