Primary (at baseline, Day 1, Weeks 1, 2, 4, 8): size of lesion area by chest imaging, blood oxygen saturation
Secondary (at baseline, Day 1, Weeks 1, 2, 4, 8): rate of mortality within 28‐days, sequential organ failure assessment, side effects in the UC‐MSCs treatment group, Electrocardiogram, the changes of ST‐T interval mostly, Concentration of C‐reactive protein C‐reactive protein, immunoglobulin, CD4 + and CD8 + T cells count, Concentration of the blood cytokine (IL‐1β, IL‐6, IL‐8,IL‐10,TNF‐α), Concentration of the myocardial enzymes