Omicron infection alters the profile of organ failure in severe COVID-19: a multicenter study comparing Omicron and the wild-type strain.

introductionThe Omicron variant of SARS-CoV-2 has exhibited altered transmissibility and virulence compared with the Wild-type strain. Currently, no research has focused on the differences in organ failure caused by the two strains. Understanding the clinical characteristics and organ failure patterns of Omicron infection is essential to improve management strategies for severe cases.

methodsThis multicenter retrospective observational study included two cohorts: the Omicron cohort, consisting of 7,000 COVID-19 patients admitted to 10 national research centers in China from December 2022 to January 2023, and the Wild-type cohort, consisting of 733 patients from designated hospitals during the early outbreak in 2020. Demographic, clinical, laboratory, and treatment data were collected and analyzed. We compared the differences in patient characteristics, developments of organ dysfunction and outcomes between the two cohorts. Multivariate logistic regression models were employed to identify risk factors for severe COVID-19 and death.

resultsThe Omicron cohort included 7000 patients, 1551 (22.2%) of whom had severe cases. The median age of the patients was 73.0 [60.0, 84.0] years, with 4319 male patients (61.7%). Regarding underlying comorbidities, 5305 patients (75.7%) presented with at least one chronic condition, most frequently hypertension (46.0%) and diabetes mellitus (26.3%). The overall in-hospital mortality rate was 15.5%, and 5666 patients (80.9%) experienced at least one organ dysfunction, with respiratory failure being the most prevalent (72.6%). Compared with the Wild-type cohort, severe Omicron patients were older, had a greater proportion of males, and more comorbidities. Severe Omicron cases showed a distinct pattern characterized by a higher prevalence of extrapulmonary organ dysfunction, particularly kidney failure. Multivariate analysis identified older age, male sex, lack of vaccination, preadmission corticosteroid use, and comorbidities as independent predictors of severe disease. Among severe patients, older age, malignancy, hypoxemia, thrombocytopenia, and elevated troponin were independent predictors of mortality.

conclusionAfter the widespread emergence of Omicron, severe COVID-19 predominantly affected older patients with multiple comorbidities and showed a different organ failure spectrum, with greater extrapulmonary involvement, particularly kidney failure, in the early phase of hospitalization. These findings highlight the evolving clinical and pathophysiological features of COVID-19 in the Omicron era. CLINICAL TRIAL NUMBER: Not applicable.