Impact of nirsevimab immunization on admissions at a tertiary hospital

The efficacy of nirsevimab for the prevention of respiratory syncytial virus (RSV) infection has shown good real-life results. The objective was to investigate the impact of a nirsevimab immunisation strategy on admissions due to RSV and bronchiolitis caused by other viruses in a tertiary care hospital.

Cohort study comparing the cumulative incidence of admissions due to RSV and other respiratory viruses in a tertiary care hospital in two consecutive epidemic seasons. The population of the second season underwent a population-based intervention consisting of the administration of nirsevimab to newborns and children under 6 months of age (intervention group), which did not occur in the first season (control group). Frequency and association measures were calculated.

Immunization coverage was 93.8% in maternity wards and 89.2% in primary care. During the intervention season, 40 infants under 6 months of age were admitted compared to 147 during the control season, with a percentage of admissions to the Intensive Care Unit (ICU) of 0.05% and 0.6%, respectively. The RRR was 70.7% (IC 95: 57,2 a 80) in infants aged 1-6 months, 80.6% (IC 95: 53,7 a 91,9) in newborns, and 90.9% (IC 95: 29,8 a 98,8) in the ICU. No newborns from January to March of either season were admitted with RSV infection. The RR for rhinovirus and metapneumovirus bronchiolitis during the intervention season was 1.52 (IC 95: 1,17 a 1,98) and 1.66 (IC 95: 1,35 a 2,04), respectively.

The reduction in RSV admissions in a tertiary hospital, after immunisation with nirsevimab in real-life settings is significant, and is more significant in neonatal units and ICUs. Immunisation in maternity wards from January to March had no impact. The increased RR of hospitalisation due to rhinovirus and metapneumovirus bronchiolitis requires further studies to infer causality.