1. onset of symptoms of covid-19 \>14 days. 2. pregnant or nursing (lactating) women. 3. hospitalized \>10 days for covid-19. 4. need of high concentration non-rebreather mask, high-flow nasal cannula , non-invasive mechanical ventilation or invasive mechanical ventilation. 5. systolic blood pressure \< 90 mmhg. 6. serious concomitant illness. 7. recent treatment with cell-depleting therapies. 8. enrolled in another clinical trial. 9. severe renal dysfunction. 10. in the opinion of the investigator, unable to comply with the requirements to participate in the study.

1. onset of symptoms of covid-19 \>14 days. 2. pregnant or nursing (lactating) women. 3. hospitalized \>10 days for covid-19. 4. need of high concentration non-rebreather mask, high-flow nasal cannula , non-invasive mechanical ventilation or invasive mechanical ventilation. 5. systolic blood pressure \< 90 mmhg. 6. serious concomitant illness. 7. recent treatment with cell-depleting therapies. 8. enrolled in another clinical trial. 9. severe renal dysfunction. 10. in the opinion of the investigator, unable to comply with the requirements to participate in the study.

onset of symptoms of covid-19 >14 days. pregnant or nursing (lactating) women. hospitalized >10 days for covid-19. need of high concentration non-rebreather mask, high-flow nasal cannula , non-invasive mechanical ventilation or invasive mechanical ventilation. systolic blood pressure < 90 mmhg. serious concomitant illness. recent treatment with cell-depleting therapies. enrolled in another clinical trial. severe renal dysfunction. in the opinion of the investigator, unable to comply with the requirements to participate in the study.

onset of symptoms of covid-19 >14 days. pregnant or nursing (lactating) women. hospitalized >10 days for covid-19. need of high concentration non-rebreather mask, high-flow nasal cannula , non-invasive mechanical ventilation or invasive mechanical ventilation. systolic blood pressure < 90 mmhg. serious concomitant illness. recent treatment with cell-depleting therapies. enrolled in another clinical trial. severe renal dysfunction. in the opinion of the investigator, unable to comply with the requirements to participate in the study.