The disease severity of COVID-19 caused by Omicron variants: A brief review.

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in November 2021 and spread worldwide. This review summarizes the reported mortality and morbidity rates of coronavirus disease (COVID-19) caused by Omicron variants. In 21 previous studies, the mortality of patients infected with Omicron variants ranged from 0.01 to 13.1%, whereas that of those infected with previous variants was from 0.08% to 29.1%. The proportions of intensive care unit admissions and mechanical ventilation were lower for Omicron variants than for the previous variants. Future studies should clarify the mechanisms of transmissibility and severity of COVID-19 caused by the Omicron variants.