question: In this clinical research project, we will conduct a highly rigorous clinical trial where we randomize the patients between umbilical cord (UC)-derived mesenchymal stem cell (MSC) and standard of care (SOC). This study will ask the question whether the allogenic MSCs are effective in reducing death and/or progression of COVID-19 disease when administered to patients with moderate to severe symptoms. MSCs are unique group of cells with minimal immune reactivity and produce multiple beneficial effects, which include reduction of severe inflammatory reaction. There is convincing evidence from human studies that intravenous (IV) delivery of MSCs can directly impact the hyper-inflammatory responses of COVID-19 induced injury of the heart and lungs. Our study will evaluate the safety and efficacy of allogenic UC-derived MSCs administered intravenously to COVID-19 patients with moderate to severe symptom in a randomized, controlled clinical trial. In addition, we will determine whether : (i) UC-derived MSCs are effective in reducing 30-day all-cause mortality (primary endpoint) and (ii) UC-derived MSCs are effective in preventing progression to mechanical ventilation, and/or reducing an inflammatory response, and/or improving overall patient condition (secondary endpoints).