Clinical features and outcomes in adults with COVID-19 during the pre-Omicron and Omicron waves

•The death rate for Omicron inpatients (n = 1142) was 11 % vs16.9 % for pre-Omicron inpatients (n = 1690)•Independent risk factors for death included unvaccinated status and comorbidities.•Type of variant was not an independent risk factor for death.•Omicron inpatients had fewer comorbidities but were more frequently immunosuppressed.•Nosocomial COVID-19 was more frequent during Omicron waves (18.2% vs15.4%)