Treatment of Respiratory Complications Associated With COVID-19 Using Umbilical Cord Mesenchymal Stromal Cells

Inclusion Criteria: * Male or female, aged 18 years-old or older * Laboratory-confirmed SARS-CoV-2 infection determined by reverse-transcription polymerase chain reaction (RT-PCR) prior to randomization * Hospitalized patients * Severe COVID-19 pneumonia defined as patients who cannot saturate \> 96% on 4 L/min but are NOT on "non-invasive" ventilation nor invasive mechanical ventilation nor Extracorporeal membrane oxygenation (ECMO). Patients on high flow would be eligible if they receive treatment in a non-critical care unit only. * Use of contraception or acceptable birth control for the duration of the study in women of childbearing potential * Provision of written or verbal informed consent by the patient or designated substitute decision maker Exclusion Criteria: * Inability to provide informed consent * Patients expected to survive less than 24 hours * Advanced directives of patient's wishes to refuse intubation. * Patients on mechanical ventilation * Pregnant women \[pregnancy defined as the state of a female after conception and until the termination of gestation, confirmed by a positive human chorionic gonadotrophin (hCG) laboratory test\] * Breastfeeding * Weight \> 100 kg or \< 50 kg * Cancer not in remission or active serious illness unrelated to COVID-19. * Any of the following laboratory results at screening: Absolute neutrophil count (ANC) ≤ 1.0 x 109/L, Platelets (PLT) \< 50 G /L, Alanine transaminase (ALT) or Aspartate transaminase (AST) \> 5N, eGFR \< 30 mL/min * Current documented bacterial infection * Known infection with Human immunodeficiency virus, Treponema pallidum, Hepatitis B antigen (serology consistent with previous vaccination and a history of vaccination is acceptable) or Hepatitis C * On-going therapy against tuberculosis, or exposed to tuberculosis or have travelled in areas with high risk of tuberculosis or mycosis within the last 3 months * Known allergies to a component of the ProTrans® product * Pre-existing chronic respiratory diseases requiring long-term oxygen therapy or severe pulmonary hypertension (PAPS \>30 mm HG) or pulmonary fibrosis * Pre-existing cirrhosis with basal Child and Pugh of C