Table 1 Inclusion and exclusion criteria

• Available informed consent

• Male or female, 18–70 years of age

• Evidence of pneumonia by chest X-ray or CT scan and/or confirmation of SARS-CoV-2 by qRT-PCR

• ARDS diagnosed and SpO2/FiO2 ≤ 315

• SOFA score between 2 and 13

• Required mechanical ventilation and/or supplemental oxygen

• Presence of severe allergic reaction after stem cell infusion

• Psychosis or under treatment for malignancy

• Co-infection with HIV, tuberculosis, adenovirus, or other respiratory infections virus

• Patient with previous history of pulmonary embolism

• Anticipated death within 48 h

• Continuous use of immunosuppressive agents or organ transplant within the past 6 months

• Pregnancy or breastfeeding