Estimating the disease burden of respiratory syncytial virus (RSV) in older adults in England during the 2023/24 season: a new national hospital-based surveillance system

BackgroundRespiratory syncytial virus (RSV) is an important cause of acute respiratory infection (ARI) in older adults. Vaccines that protect against severe RSV infection are now available. AimWe aimed to describe the incidence, presentation, severity and clinical outcomes of RSV-associated ARI in hospitalised older adults using a new Hospital-based ARI Sentinel Surveillance (HARISS) system in England in the winter prior to RSV vaccine introduction. MethodsAdults aged [≥]65 years from seven hospitals admitted for [≥]24 hours with symptomatic ARI were included. Three groups were identified: RSV positive; influenza positive; negative for RSV, influenza and SARS-CoV-2. We estimated the hospitalisation rate of RSV-associated ARI compared to influenza-associated ARI and assessed clinical outcomes using Poisson regression and mortality using Cox regression across groups. ResultsThis surveillance study included 2743 adults. During the 2023/4 season the hospitalisation rate for RSV-associated ARI was 58.3 per 100,000, compared to 114.6 per 100,000 for influenza-associated ARI. Hospitalisation rates increased with age. Exacerbation of chronic illness including lung disease, heart disease or frailty was a frequent cause of admission in RSV-associated ARI, with a combined incidence of 33.1 per 100,000. The majority of adults with RSV-associated ARI had at least one comorbidity (81%); a high proportion with immunosuppression (26%). Symptoms and clinical outcomes including mortality were similar between RSV- and influenza-associated ARI; 30-day mortality 10.6% vs 8.7% (adjusted hazard ratio 0.85,95% confidence interval 0.6-1.2). ConclusionIn England, RSV infection is a common cause of hospitalisation in older adults. Symptoms at presentation, severity and clinical outcomes, including mortality, are comparable to influenza.