Universal administration of nirsevimab in infants: an analysis of hospitalisations and paediatric intensive care unit admissions for RSV-associated lower respiratory tract infections.

The aim of this study was to assess the impact of universal nirsevimab administration on hospitalisations and paediatric intensive care unit (PICU) admissions due to lower respiratory tract infection associated with respiratory syncytial virus (RSV-LRTI). An observational study was conducted at a tertiary hospital in Spain to compare the frequency and characteristics of children under five years of age hospitalised for RSV-LRTI between October 2023 and March 2024 (nirsevimab period), with the data from two prepandemic COVID- 19 seasons (2018-2019 and 2019-2020) and one postpandemic season (2022-2023). A total of 311 patients were included in the study. During the nirsevimab period, a decrease in the number of children hospitalised for RSV-LRTI was observed, particularly for children under six months of age. Compared with the prepandemic period, there was an 83.3% decrease in hospitalisations and a 73.3% reduction in PICU admissions in this age group. Similarly, compared with the postpandemic period, there was a 90.8% reduction in hospitalisations and an 87.9% reduction in PICU admissions. Furthermore, the median age was greater (15.6 months; IQR 11.1-27.3) than it was in the prepandemic period (4 months; IQR 1.6-8.9) and postpandemic period (3.4 months; IQR 1.5-10.6) (p < 0.001). Moreover, the length of hospital stay during the nirsevimab period (4 days; IQR 3-6) was shorter than that observed during the prepandemic period (6 days; IQR 4-9) and the postpandemic period (5 days; IQR 3-8) (p = 0.003).Conclusions: Following the introduction of universal immunoprophylaxis with nirsevimab, notable reductions in hospitalisations and PICU admissions due to RSV-LRTI were observed among young infants. This resulted in a shift in the age profile and a shorter length of hospital stay. What Is Known • Nirsevimab is a novel humanised IgG1 monoclonal antibody with a prolonged half-life that has been demonstrated to reduce RSV-associated hospitalisations in controlled clinical trials; however, real-world data are still limited. What Is New: • The findings of the present study corroborate the effectiveness of nirsevimab. Following the implementation of universal immunoprophylaxis with nirsevimab, a notable reduction in hospitalisations and admissions to the paediatric intensive care unit for RSV-associated lower respiratory tract infections was observed, particularly among infants younger than 6 months, who have been the main target of this passive immunisation strategy. In addition, the patients admitted were older and the length of hospital stay was shorter.