Severe allergies or allergies after 1st injection to stem cell preparations and their components Patients with a malignant tumor, other serious systemic diseases, and psychosis Co-Infection of HIV, tuberculosis, influenza virus, adenovirus and other respiratory infection virus Patients with previous history of pulmonary embolism Be thought by researchers to be inappropriate to participate in this clinical study (Expected deaths within 48 hours, uncontrolled infections) Liver or kidney SOFA score of more than 3 points; combined with other organ failure (need organ support), Stage 4 severe chronic kidney disease or requiring dialysis (i.e. estimated glomerular filtration rate (eGFR) < 30) Pulmonary obstructive pneumonia, severe pulmonary interstitial fibrosis, alveolar proteinosis, allergic alveolitis, and other known viral pneumonia or bacterial pneumonia Continuous use of immunosuppressive agents or organ transplants in the past 6 months In vitro life support (ECMO, ECCO2R, RRT) Pregnant or lactating women Uncontrolled underling disease

Severe allergies or allergies after 1st injection to stem cell preparations and their components Patients with a malignant tumor, other serious systemic diseases, and psychosis Co-Infection of HIV, tuberculosis, influenza virus, adenovirus and other respiratory infection virus Patients with previous history of pulmonary embolism Be thought by researchers to be inappropriate to participate in this clinical study (Expected deaths within 48 hours, uncontrolled infections) Liver or kidney SOFA score of more than 3 points; combined with other organ failure (need organ support), Stage 4 severe chronic kidney disease or requiring dialysis (i.e. estimated glomerular filtration rate (eGFR) < 30) Pulmonary obstructive pneumonia, severe pulmonary interstitial fibrosis, alveolar proteinosis, allergic alveolitis, and other known viral pneumonia or bacterial pneumonia Continuous use of immunosuppressive agents or organ transplants in the past 6 months In vitro life support (ECMO, ECCO2R, RRT) Pregnant or lactating women Uncontrolled underling disease