Methods
Medical records from 157 patients with confirmed severe COVID-19 were collected in in Hubei General Hospital during the management by national medical team. A flow chart (Figure S1) describes patient inclusion. CD3+T cells count, CD4+T cells count, CD8+T cells count and lymphocyte count were classified as low group and high group according to the laboratory reference values (low group: CD4+T<404 cells/ul). The study was registry with clinicaltrials.gov identifier NCT04292964. All study procedures were approved by the local ethics committee (approval NO. 20200701). All patients in the study were followed up from admission till death or discharge. The outcome was defined as the in-hospital death rate.