Respiratory syncytial virus-associated hospitalization in children aged <2 years in Spain from 2018 to 2021.

Respiratory syncytial virus (RSV) is the leading cause of severe respiratory infections in children. In many countries, changes in RSV hospitalizations have occurred during COVID-19 restriction, with alterations in annual pre-pandemic trends. The objective of this retrospective study was to describe the epidemiology of RSV during the pandemic in Spain (2018-2021) through population-based estimates of hospitalization in children <2 years old. A total of 56,741 hospital discharges were identified with a 2.2% decrease between the beginning and the end of the COVID-19 pandemic resulting in a hospitalization rate of 1,915.89 (95% CI = 1,900.13-1,931.65) hospitalizations per 100,000 children. During the four-year period, a total of 34 deaths were recorded (males 63%, females 37%). The average annual cost to the National Health-Care System of bronchiolitis requiring hospitalization was €49,6 million with an average hospitalization cost per case of €3,054. RSV is a very frequent virus associated with community-acquired pneumonia (CAP) in children under 2 years old, so future preventive interventions should target this age group including vaccination programs.