Factors associated with severe health outcomes among community-dwelling older adults hospitalized with respiratory syncytial virus

Objectives We describe the burden of respiratory syncytial virus (RSV)-related hospitalization among community-dwelling older adults in the pre-vaccine era and identify factors associated with adverse hospital outcomes. Methods We conducted a population-based retrospective cohort study among adults aged ≥50 years hospitalized with RSV, using linked laboratory and health administrative data in Ontario, Canada during 2017-2020. We used modified Poisson regression models to assess associations between 25 individual factors and four hospital-related outcomes (30-day mortality, intensive care unit [ICU] utilization, hospital length of stay [LOS], and 30-day readmission). Results Of 3,221 adults hospitalized with RSV, 314 (9.7%) died within 30 days, 560 (17.4%) required ICU care , and the median (interquartile range) LOS was 6 (3-11) days. Of 2,913 adults discharged alive, 343 (11.8%) were readmitted within 30 days. Frailty strongly predicted all outcomes: mortality (adjusted risk ratio [aRR]=1.36; 95%CI, 1.05–1.76), ICU (aRR=1.45; 95%CI, 1.22–1.73), LOS (adjusted incidence rate ratio [IRR]=1.96; 95%CI, 1.81–2.12), and readmission (aRR=1.46; 95%CI, 1.14–1.87). Adults aged ≥90 years (aRR=2.37; 95%CI, 1.32–4.24), those with active cancer (aRR=1.63; 95%CI, 1.17–2.27) or other immunodeficiencies (aRR=1.54; 95%CI, 1.21–1.95), and chronic home care recipients (aRR=1.32; 95%CI, 1.03–1.67) had a higher risk of mortality, with similar trends observed for readmission. Conclusions RSV causes substantial morbidity and mortality among hospitalized older adults. These findings help identify high-risk groups for vaccine prioritization.