Inclusion Criteria:  A written, signed informed consent, or emergency oral consent, by the patient or the patient's legally authorized representative, and the anticipated ability for participant to be re-consented in the future for ongoing Study participation Men and women aged ≥ 25 - 80 (included) years of age Hospitalized patients with two absolute lymphocyte count (ALC) ≤ 1000 cells/mm3, at two time points at least 24 hours apart, following HOSPITALIZATION: Hospitalized patients with moderate to severe hypoxemia requiring oxygen therapy at >4L per minute nasal cannula or greater to keep saturations >90%, non-invasive positive pressure ventilation (e.g., BIPAP), or patients intubated / ventilated for respiratory failure Confirmed infection with COVID-19 by any acceptable test available / utilized at each site Willingness and ability to practice contraception regardless of the gender of the patient during 5 months after last drug exposure Private insurance or government / institution financial support (through CMS or other)  Exclusion Criteria:  Pregnancy or breast feeding ALT and/or AST > 5 x ULN Known, active auto-immune disease; Ongoing cancer treatment with chemotherapy / immunotherapy or any cancer therapy within last 3 months and/or ongoing Patients with past history of Solid Organ transplant Active tuberculosis, uncontrolled active HBV or HCV infection, HIV with positive viral load Hospitalized patients with refractory hypoxia, defined as inability to maintain saturation >85% with maximal available therapy for >6 hours Patients receiving any agent with immune suppressive effects, other than steroids at dosages less than 300 mg/day equivalent hydrocortisone and/or anti-IL-6R treatments like Tocilizumab or Sarilumab or anti-IL-1 treatment like Anakinra which should preferably be minimized Patients with baseline Rockwood Clinical Frailty Scale ≥ 6 at Hospital admission Patients showing an increase of the NEWS2 score by more than 6 points during the screening/ baseline period (48 to 72 hrs prior to first administration) Patients under guardianship