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Updated: Jun 4, 2025
An Improved and High Throughput Respiratory Syncytial Virus RSV Micro-neutralization Assay
Published on: January 26, 2019
Changes in Respiratory Syncytial Virus-Associated Hospitalisations Epidemiology After Nirsevimab Introduction in
Cécile Chauvel1,2, Côme Horvat3, Etienne Javouhey3,4
1Center of Excellence in Respiratory Pathogens (CERP), Hospices Civils de Lyon (HCL), Lyon, France.
Background:
Respiratory Syncytial Virus (RSV) is a major health concern, particularly for infants. In France, Nirsevimab, a long-acting monoclonal antibody to prevent RSV-associated lower respiratory tract infections (LRTI) was available from September 2023. We described RSV-associated LRTI hospitalisations during the 2023-2024 season among infants younger than six months born at the Hospices Civils de Lyon (HCL), and evaluated the effectiveness of Nirsevimab against RSV-LRTI hospitalisation.
Methods:
This observational study included infants born and hospitalised at the HCL during the 2023-2024 season, along with pre-COVID-19 and 2022-2023 seasons. Information on Nirsevimab immunisation status, clinical and perinatal variables were collected through routine care. Infants' characteristics and incidence rate of hospitalisation per 100 births during 2023-2024 were compared with the historical periods overall and by delay between birth and the onset of the RSV season. Nirsevimab effectiveness was computed by the screening method.
Results:
During the 2023-2024 season, 83 infants younger than six months were hospitalised with an RSV-associated LRTI. Compared with the historical periods (640 pre-COVID-19 and 123 in 2022-2023), these infants were older. Incidence rate for infants born during the period when immunisation was available were lower than the previous seasons; incidence rate ratios were 0.45 (95% confidence interval [CI]: 0.33; 0.62) in 2023-2024 compared with pre-COVID-19 period and 0.53 (95%CI: 0.36; 0.77) compared with 2022-2023 season. Nirsevimab effectiveness was 78.3% (95%CI: 55.9; 89.5) with a coverage of 79.3% in the two main HCL maternities.
Conclusions:
High Nirsevimab coverage and effectiveness were estimated in a real-world setting. A change in the age distribution of RSV-associated LRTI hospitalisations in 2023-2024 was noted compared with historical seasons.
