Changes in Respiratory Syncytial Virus-Associated Hospitalisations
Epidemiology After Nirsevimab Introduction in Lyon, France
Abstract
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 risk 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 these infants were older. Incidence risk for
infants born during the period when immunisation was available were
lower than the previous seasons; incidence risk 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 HCL maternities. Conclusions:
This study revealed a change in the epidemiology of RSV-associated LRTI
hospitalisations in 2023-2024. High coverage and effectiveness were
estimated in real-world setting.