Mortality Risk Among Patients Hospitalized Primarily for COVID-19 During the Omicron and Delta Variant Pandemic Periods — United States, April 2020–June 2022
Stacey Adjei, Kai Hong, Noelle‐Angelique Molinari, Lara Bull–Otterson, Umed A. Ajani, Adi V. Gundlapalli, Aaron M. Harris, Joy Hsu, Sameer S. Kadri, Jon Starnes, Kristin Yeoman, Tegan K. Boehmer
Abstract
The risk for COVID-19-associated mortality increases with age, disability, and underlying medical conditions (1). Early in the emergence of the Omicron variant of SARS-CoV-2, the virus that causes COVID-19, mortality among hospitalized COVID-19 patients was lower than that during previous pandemic peaks (2-5), and some health authorities reported that a substantial proportion of COVID-19 hospitalizations were not primarily for COVID-19-related illness,* which might account for the lower mortality among hospitalized patients. Using a large hospital administrative database, CDC assessed in-hospital mortality risk overall and by demographic and clinical characteristics during the Delta (July-October 2021), early Omicron (January-March 2022), and later Omicron (April-June 2022) variant periods among patients hospitalized primarily for COVID-19. Model-estimated adjusted mortality risk differences (aMRDs) (measures of absolute risk) and adjusted mortality risk ratios (aMRRs) (measures of relative risk) for in-hospital death were calculated comparing the early and later Omicron periods with the Delta period. Crude mortality risk (cMR) (deaths per 100 patients hospitalized primarily for COVID-19) was lower during the early Omicron (13.1) and later Omicron (4.9) periods than during the Delta (15.1) period (p<0.001). Adjusted mortality risk was lower during the Omicron periods than during the Delta period * Examples include New York (https://www.wivb.com/news/new-york/new-yorkstate-covid-19-update-saturday-january-22/); Massachusetts (https://www. boston.com/news/coronavirus/2022/01/21/almost-half-of-mass-covidhospitalizations-are-now-classified-as-incidental-heres-what-that-means/); Marin County, California (https://coronavirus.marinhhs.org/ surveillance#keyindicators); and various health systems in Florida, Maryland, and Texas (https://www.nytimes.com/2022/01/04/health/covid-omicronhospitalizations.html).