Comparison of the Characteristics of Patients Admitted to the Intensive Care Unit During Peak Periods of SARS-CoV-2 Variants

Background: Since its emergence, SARS-CoV-2 has undergone numerous mutations. The World Health Organization (WHO) has identified key variants, including Ancestral, Beta, Delta and Omicron. Clinical characteristics and mortality have varied between these variants. This study evaluated the clinical features and outcomes of SARS-CoV-2-positive patients admitted to the Intensive Care Unit (ICU) during different peak periods. Methods: Türkiye experienced four major COVID-19 waves, defined by the Ministry of Health: the first (November 2020-January 2021), second (February-May 2021), third (July-November 2021) and fourth (December 2021-March 2022). Patients admitted to the ICU during these waves were included. Demographics, comorbidities, oxygen therapy, ventilation type, ICU length of stay and mortality rates were analyzed. Results: A total of 510 patients were evaluated: 61 (12%) in the first wave, 148 (29%) in the second, 187 (37%) in the third and 114 (22%) in the fourth. The median age was 70 years (Interquartile range [IQR]: 21), lowest in the second wave (62) and highest in the fourth (76). Most patients (75%, n=384) were unvaccinated. Overall ICU mortality was 81%, ranging from 66% in the first wave to 86% in the fourth. ICU stay length was similar across waves. Conclusion: COVID-19 ICU patient characteristics and outcomes varied across different variants. Further studies are needed to clarify whether Omicron is less pathogenic compared with earlier strains.