* (1) known or suspected allergy to the components of azvudine tablets; (2) patients diagnosed as severe or critical covid-19 infection (severe: 1. shortness of breath with rr ≥ 30 breaths/min; 2. oxygen saturation ≤ 93% when inhaling air at rest; 3. partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤ 300 mmhg; 4. progressive worsening of clinical symptoms, and obvious lesion progression \> 50% on lung images within 24 to 48 hours. critical: 1. respiratory failure, requiring mechanical ventilation; 2. shock; 3. concomitant organ failure, requiring care in icu); (3) patients with severe liver disease (total bilirubin \[tbil\] ≥ 2 × upper limit of normal (uln), alanine aminotransferase (alt) and aspartate aminotransferase (ast) ≥ 3 × uln; (4) patients with severe renal insufficiency (glomerular filtration rate ≤ 60 ml/min/1.73 m2) or currently on continuous renal replacement therapy, hemodialysis, and/or peritoneal dialysis; (5) patients with malabsorption syndrome or any other condition compromising gastrointestinal absorption, or patients requiring parenteral nutrition or with difficulty in taking the investigational product orally; (6) known hiv infection; (7) presence of diabetic ketosis or hyperosmolar hyperglycemic state (hhs); (8) total neutrophil count \< 750 cells/l; (9) pregnant or lactating women or those who plan to have a child during participation in this study and within six months after the end of this study; (10) currently participating in another clinical trial or currently using another investigational product; (11) presence of other active infections (must be etiologically confirmed) in addition to covid-19 infection; (12) presence of any comorbidities requiring hospitalization and/or a surgical procedure within 7 days prior to the start of this study or a comorbidity considered life-threatening within 30 days prior to the start of this study; (13) patients who have received or are expected to receive convalescent plasma for covid-19; (14) previous treatment with anti-viral agents that have been proved to be effective against covid-19, including but not limited to nirmatrelvir/ritonavir or molnupiravir (this criterion does not apply to use of glucocorticoids for reasons other than covid-19); (15) other conditions that make it inappropriate for the participant to take part in this trial at the investigator's discretion.

* (1) known or suspected allergy to the components of azvudine tablets; (2) patients diagnosed as severe or critical covid-19 infection (severe: 1. shortness of breath with rr ≥ 30 breaths/min; 2. oxygen saturation ≤ 93% when inhaling air at rest; 3. partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤ 300 mmhg; 4. progressive worsening of clinical symptoms, and obvious lesion progression \> 50% on lung images within 24 to 48 hours. critical: 1. respiratory failure, requiring mechanical ventilation; 2. shock; 3. concomitant organ failure, requiring care in icu); (3) patients with severe liver disease (total bilirubin \[tbil\] ≥ 2 × upper limit of normal (uln), alanine aminotransferase (alt) and aspartate aminotransferase (ast) ≥ 3 × uln; (4) patients with severe renal insufficiency (glomerular filtration rate ≤ 60 ml/min/1.73 m2) or currently on continuous renal replacement therapy, hemodialysis, and/or peritoneal dialysis; (5) patients with malabsorption syndrome or any other condition compromising gastrointestinal absorption, or patients requiring parenteral nutrition or with difficulty in taking the investigational product orally; (6) known hiv infection; (7) presence of diabetic ketosis or hyperosmolar hyperglycemic state (hhs); (8) total neutrophil count \< 750 cells/l; (9) pregnant or lactating women or those who plan to have a child during participation in this study and within six months after the end of this study; (10) currently participating in another clinical trial or currently using another investigational product; (11) presence of other active infections (must be etiologically confirmed) in addition to covid-19 infection; (12) presence of any comorbidities requiring hospitalization and/or a surgical procedure within 7 days prior to the start of this study or a comorbidity considered life-threatening within 30 days prior to the start of this study; (13) patients who have received or are expected to receive convalescent plasma for covid-19; (14) previous treatment with anti-viral agents that have been proved to be effective against covid-19, including but not limited to nirmatrelvir/ritonavir or molnupiravir (this criterion does not apply to use of glucocorticoids for reasons other than covid-19); (15) other conditions that make it inappropriate for the participant to take part in this trial at the investigator's discretion.

(1) known or suspected allergy to the components of azvudine tablets; (2) patients diagnosed as severe or critical covid-19 infection (severe: 1. shortness of breath with rr ≥ 30 breaths/min; 2. oxygen saturation ≤ 93% when inhaling air at rest; 3. partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤ 300 mmhg; 4. progressive worsening of clinical symptoms, and obvious lesion progression > 50% on lung images within 24 to 48 hours. critical: 1. respiratory failure, requiring mechanical ventilation; 2. shock; 3. concomitant organ failure, requiring care in icu); (3) patients with severe liver disease (total bilirubin [tbil] ≥ 2 × upper limit of normal (uln), alanine aminotransferase (alt) and aspartate aminotransferase (ast) ≥ 3 × uln; (4) patients with severe renal insufficiency (glomerular filtration rate ≤ 60 ml/min/1.73 m2) or currently on continuous renal replacement therapy, hemodialysis, and/or peritoneal dialysis; (5) patients with malabsorption syndrome or any other condition compromising gastrointestinal absorption, or patients requiring parenteral nutrition or with difficulty in taking the investigational product orally; (6) known hiv infection; (7) presence of diabetic ketosis or hyperosmolar hyperglycemic state (hhs); (8) total neutrophil count < 750 cells/l; (9) pregnant or lactating women or those who plan to have a child during participation in this study and within six months after the end of this study; (10) currently participating in another clinical trial or currently using another investigational product; (11) presence of other active infections (must be etiologically confirmed) in addition to covid-19 infection; (12) presence of any comorbidities requiring hospitalization and/or a surgical procedure within 7 days prior to the start of this study or a comorbidity considered life-threatening within 30 days prior to the start of this study; (13) patients who have received or are expected to receive convalescent plasma for covid-19; (14) previous treatment with anti-viral agents that have been proved to be effective against covid-19, including but not limited to nirmatrelvir/ritonavir or molnupiravir (this criterion does not apply to use of glucocorticoids for reasons other than covid-19); (15) other conditions that make it inappropriate for the participant to take part in this trial at the investigator's discretion.

(1) known or suspected allergy to the components of azvudine tablets; (2) patients diagnosed as severe or critical covid-19 infection (severe: 1. shortness of breath with rr ≥ 30 breaths/min; 2. oxygen saturation ≤ 93% when inhaling air at rest; 3. partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤ 300 mmhg; 4. progressive worsening of clinical symptoms, and obvious lesion progression > 50% on lung images within 24 to 48 hours. critical: 1. respiratory failure, requiring mechanical ventilation; 2. shock; 3. concomitant organ failure, requiring care in icu); (3) patients with severe liver disease (total bilirubin [tbil] ≥ 2 × upper limit of normal (uln), alanine aminotransferase (alt) and aspartate aminotransferase (ast) ≥ 3 × uln; (4) patients with severe renal insufficiency (glomerular filtration rate ≤ 60 ml/min/1.73 m2) or currently on continuous renal replacement therapy, hemodialysis, and/or peritoneal dialysis; (5) patients with malabsorption syndrome or any other condition compromising gastrointestinal absorption, or patients requiring parenteral nutrition or with difficulty in taking the investigational product orally; (6) known hiv infection; (7) presence of diabetic ketosis or hyperosmolar hyperglycemic state (hhs); (8) total neutrophil count < 750 cells/l; (9) pregnant or lactating women or those who plan to have a child during participation in this study and within six months after the end of this study; (10) currently participating in another clinical trial or currently using another investigational product; (11) presence of other active infections (must be etiologically confirmed) in addition to covid-19 infection; (12) presence of any comorbidities requiring hospitalization and/or a surgical procedure within 7 days prior to the start of this study or a comorbidity considered life-threatening within 30 days prior to the start of this study; (13) patients who have received or are expected to receive convalescent plasma for covid-19; (14) previous treatment with anti-viral agents that have been proved to be effective against covid-19, including but not limited to nirmatrelvir/ritonavir or molnupiravir (this criterion does not apply to use of glucocorticoids for reasons other than covid-19); (15) other conditions that make it inappropriate for the participant to take part in this trial at the investigator's discretion.