(1) known or suspected allergies to the components of azivudine tablets, (2) according to the latest version of the National Health and Medical Commission Diagnostic criteria of COVID-19, ?patients with severe novel coronavirus pneumonia was confirmed, (3) severe liver disease (TBIL>=2 times normal upper limit, ALTAST>=5 times normal upper limit), (4) subjects with severe renal insufficiency (glomerular filtration rate =60 mL/min/1.73 m2) or undergoing continuous renal replacement therapy, hemodialysis or peritoneal dialysis, (5) subjects with complication of malabsorption syndrome or any other condition affecting gastrointestinal absorption, requiring intravenous nutrition or not being able to take drugs orally, (6) subjectsis currently receiving anti-hiv treatment, (7)women who are breast-feeding during pregnancy or have a family plan during the trial period and within 6 months after the end of the trial, (8) participating in other clinical trials or using experimental drugs, except traditional Chinese medicine, (9) Other conditions that not appropriate to be enrolled into this study based on investigator's advise.

(1) known or suspected allergies to the components of azivudine tablets, (2) according to the latest version of the National Health and Medical Commission Diagnostic criteria of COVID-19, ?patients with severe novel coronavirus pneumonia was confirmed, (3) severe liver disease (TBIL>=2 times normal upper limit, ALTAST>=5 times normal upper limit), (4) subjects with severe renal insufficiency (glomerular filtration rate =60 mL/min/1.73 m2) or undergoing continuous renal replacement therapy, hemodialysis or peritoneal dialysis, (5) subjects with complication of malabsorption syndrome or any other condition affecting gastrointestinal absorption, requiring intravenous nutrition or not being able to take drugs orally, (6) subjectsis currently receiving anti-hiv treatment, (7)women who are breast-feeding during pregnancy or have a family plan during the trial period and within 6 months after the end of the trial, (8) participating in other clinical trials or using experimental drugs, except traditional Chinese medicine, (9) Other conditions that not appropriate to be enrolled into this study based on investigator's advise.