Burden of disease of respiratory syncytial virus in older adults and adults considered at high risk of severe infection.

Background: Availability of new vaccines for adults has increased interest in understanding Canada's respiratory syncytial virus (RSV) burden in older adults and adults considered at high risk of severe infection. Objective: To characterize the burden of RSV disease in Canada by joint analysis of the published literature and hospitalization data from a healthcare administrative database. Methods: Electronic databases of published literature were searched to identify studies and systematic reviews reporting data on outpatient visits, hospitalizations, intensive care unit (ICU) admissions and deaths associated with RSV infection in adults. For the hospitalization data analysis, hospital discharge records were extracted from the Canadian Institute of Health Information Discharge Abstract Database for all patients admitted to an acute care facility for RSV infection defined by ICD-10 codes from 2010 to 2020 and 2021 to 2023. Results: Overall, 26 studies, including seven systematic reviews, were identified and summarized. Evidence suggests that medically attended RSV respiratory tract infections (RTI) are frequently causing 4.7%-7.8% of symptomatic RTI in adults 60 years of age and older. Incidence of RSV RTI increases with age and presence of underlying medical conditions. This trend was consistently observed across all RSV clinical outcomes of interest. Patients who reside in long-term care or other chronic care facilities have a higher likelihood of severe clinical outcomes compared to patients with other living situations upon hospital admission. Approximately 10% of older adults hospitalized with RSV infection require ICU admission. Although data are limited, the case fatality ratio (CFR) among those admitted to hospital varies between 5% and 10%. Some evidence suggests that RSV burden may be close to the influenza burden in older adults. In general, the results from the Canadian hospitalization data support the rapid review findings. Rates of hospitalization, ICU admission and death associated with RSV all increased with age, with 16% of hospitalizations resulting in ICU admission and with an in-hospital CFR of 9%. Conclusion: In adults, the burden of severe RSV outcomes in general increases with age and presence of comorbidities.