Definition
COVID-19 patients and disease severity
We included all patients with confirmed COVID-19 according toDiagnosis and Treatment Protocol for Novel Coronavirus Pneumonia (trial seventh edition) by the Chinese National Health Commission11. Severity of COVID-19 was categorized into three stages: Severe cases were defined as (i) respiratory rate ≥ 30 breaths/min, (ii) oxygen saturation ≤ 93%, or (iii) PaO2/FiO2 ratio ≤ 300 mmHg. Critical cases were defined as including one or more of the following criteria: shock, respiratory failure requiring mechanical ventilation, in combination with other organ failures, or admission to ICU. Or else, other COVID patients were general cases. In-hospital disease severity were the severest grade during hospitalization.