Respiratory syncytial virus in adults aged ≥ 50 years in the Netherlands: a database and time-series modelling analysis (2013–2020)

PURPOSE: Respiratory syncytial virus (RSV) is a significant yet historically understudied contributor to acute respiratory infection (ARI) in older adults. This study aimed to quantify ARI-associated hospital admissions and estimate RSV-related burden of disease in secondary care in the Netherlands using time-series modelling. METHODS: This retrospective cohort study (1 July 2013 to 29 February 2020) utilised routinely collected primary and secondary care data from the PHARMO Data Network. ARI-associated hospital admissions in patients aged ≥ 50 years, identified via International Classification of Diseases (ICD)-10 codes, were described in terms of patient and clinical characteristics and healthcare resource utilisation. The number and annual rate of RSV- and influenza-associated ARI and lower respiratory tract disease (LRTD) hospital admissions by age and risk group were estimated using a Quasi-Poisson regression model. RESULTS: There were 97,279 ARI admissions in 63,420 patients. Estimated RSV-associated ARI hospital admission rates ranged from 0.70/1,000 person-years (PY) to 1.92/1,000 PY in adults aged ≥ 50 and ≥ 75, respectively. RSV-associated LRTD admissions varied from 0.63/1,000 PY to 1.73/1,000 PY in these groups. Hospitalisation rates were higher in high-risk individuals. Estimated RSV admissions were up to six times higher than observed. During peak months, up to 30% of ARI (20% of LRTD) admissions were attributable to RSV. RSV-coded admissions had an average length of stay of 7-8 days, and 30% of patients experienced all-cause readmission within 90 days. CONCLUSION: The substantial hospitalisation burden of RSV calls for prioritisation of RSV prevention strategies, including vaccination, alongside influenza and other causes of ARI and LRTD.