Abstract
PURPOSE: Our objective was to investigate the temporal trends in baseline characteristics, interventions, and clinical outcomes in patients hospitalized with COVID-19 in Canada over five pandemic waves. METHODS: We conducted a multicentre prospective cohort study enrolling adults and children admitted with COVID-19 from 47 Canadian hospitals. We compared characteristics, interventions, and outcomes of patients across five distinct pandemic waves. RESULTS: We enrolled 5,285 patients between 2 January 2020 and 8 February 2022. The mean (standard deviation) age was 62.6 (21.0) yr; 41.2% (n = 2,176) were female, and 48% (n = 2,539) required admission to an intensive care unit (ICU), of whom 60.3% (n = 1,530) underwent invasive mechanical ventilation. The proportion of vaccinated patients increased over time. The proportion of vaccinated hospitalized patients progressing to require ICU admission fell over pandemic waves while the proportion of unvaccinated hospitalized patients progressing to require ICU admission did not. Patients were most commonly treated with corticosteroids (48.7%; n = 2,575); use of corticosteroids and other evidence-based treatments increased over time. Hospital mortality was 22.1% (n = 1,166) among all patients, 30.2% (n = 766) among those admitted to an ICU, and 37.9% (n = 580) among those requiring invasive mechanical ventilation. Younger age, absence of chronic cardiac or pulmonary disease, severity of illness at admission, and prior vaccination was associated with a lower mortality; however, pandemic wave itself was not. CONCLUSION: Among patients hospitalized in Canada with COVID-19, several clinical factors including prior vaccination were associated with lower mortality, but pandemic wave was not.