Epidemiology of respiratory syncytial virus in a German hospital before, during and after the COVID-19 pandemic – a real world monocentric analysis over ten years

Background RSV infection affects mostly infants and induces a substantial economic and medical burden for our health care systems. To implement effective preventive strategies against RSV the knowledge about its distinct seasonality is crucial. Methods We retrospectively studied the epidemiology of RSV infection in pediatric patients admitted to a German hospital over a period of ten years by comparing their clinical data. Inclusion criterion was a laboratory confirmed RSV infection with diagnosis of bronchitis, bronchiolitis, or pneumonia. For analyses six pre-COVID years were cumulated and compared to the pandemic and post-pandemic seasons. Statistical methods included descriptive measures and exploratory tests for comparing seasons (i.e., Fisher's exact test). Results Overall, data of 1,220 children below 12 years of age (including 1,040 below 2 years) could be analyzed. The pre-COVID RSV seasons started in December and peaked in January/February. During the pandemic we detected no case in 2020/21. Season 2021/22 started in August and peaked in October, whereas the first post-pandemic season 2022/23 started in October and peaked in November. The need for intensive care and oxygen supply was significantly increased in 2022/23 compared to 2021/22. Moreover, bacterial superinfection and antibiotic treatment appeared to be significantly more frequent, also in comparison to the pre-COVID seasons. Conclusion Our study shows that the usual RSV epidemiology abruptly changed with the start of the COVID-19 epidemic. After a loss of severe RSV associated disease in 2020/21 a catch up effect could be notified in hospitalized patients in the following seasons, ending up in an almost normal season 2024/25. Future RSV monitoring is strongly recommended to calculate the hospital necessary resources, since vaccination programs, i.e., nirsevimab for infants and maternal vaccination during pregnancy, have already been started in Germany.