Clinical progression, disease severity, and mortality among adults hospitalized with COVID-19 caused by the Omicron and Delta SARS-CoV-2 variants : A population-based, matched cohort study
BACKGROUND: To compare the intrinsic virulence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron variant with the delta variant in hospitalized adults with coronavirus disease 2019 (COVID-19).METHODS: All adults hospitalized in the Capital Region of Copenhagen with a positive reverse transcription polymerase chain reaction test for SARS-CoV-2 and an available variant dete