RSV healthcare burden in adults before and since the emergence of the COVID-19 pandemic in 6 European countries

Introduction Respiratory Syncytial Virus (RSV) is a major cause of morbidity in older adults. With the emergence of the coronavirus disease 2019 (COVID-19) and the subsequent changes in respiratory viral circulation, it is crucial to reassess RSV-associated healthcare burden in adults. This study assessed RSV-associated healthcare burden in adults in six European countries before and during the COVID-19 pandemic. Methods We conducted a retrospective analysis using national hospital admissions data from Denmark, England, Finland, the Netherlands, Scotland, and regional surveillance data from the Valencia region (Spain). We included patients aged ≥18 years hospitalised for respiratory tract infections (RTIs) from 2016 to 2023. We assessed RSV-coded and laboratory-confirmed hospitalisations, intensive care unit (ICU) admissions, in-hospital length of stay (LOS), and mortality. Results RSV-associated hospitalisations significantly reduced during the 2020/2021 season across all countries, coinciding with strict COVID-19 preventive measures, but resurged in subsequent seasons. We observed the highest hospitalisation rates in adults aged ≥85 years. RSV-coded hospitalisations were found to underestimate the true burden when compared with laboratory-confirmed cases. Underestimation factors ranged from 1.1 to 4.3 times across countries. No significant differences were observed in LOS or ICU admission rates for RSV-associated hospitalisations compared to RTIs. Discussion Our findings underscore the complex epidemiology of RSV in older adults. The differences between RSV-coded and laboratory-confirmed cases highlight the critical need for improved surveillance and diagnostic practices to better assess the true burden. Our findings could be vital for guiding public health strategies, particularly with the recent introduction of RSV vaccines for older adults.