Inclusion Criteria:  Immunocompromised patients defined as  Solid organ transplant ≤1 year before inclusion or treated for acute or chronic rejection episode or Allogeneic stem cell transplant recipients ≤2 years before inclusion or treated for acute GvHD ≥grade 2 or chronic moderate-severe GvHD or Active solid or haematological oncological disease with curative perspectives or HIV infection with CD4<350 or Hypogammaglobulinemia and other severe genetic immunological defect or Auto-immune disease with biological immunosuppressive treatment* or  Other significant immunosuppressive condition such as IgG <6, treamtent with Rituximab or other biological lymphopenic treatment AND  Age ≥ 18 years old and 2 distinct ABO group determination and Positive RT-PCR for SARS-CoV-2 on a respiratory tract sample of ≤ 7 days and days post symptom onset (DPOS) ≤ 7 days at inclusion and/or No oxygen requirement (WHO 8 ordinal scale < 4): asymptomatic, mild or moderate disease, or O2 saturation ≥ 90% at room temperature and Compatible ABO donor with neutralizing antibodies (NTAB) ≥1 :160 or equivalent according to predefined antibody commercial assays cut-offs (see Study procedures) RT-PCR on a respiratory tract sample with CT value<20 or ascending kinetics at the time of infusion (highly suggested but not necessary)  Older adults defined as Age ≥ 75 years old or ≥ 65 years old with at least one co-existing condition  Arterial hypertension under pharmacological treatment Diabetes in treatment Obesity (BMI ≥ 30 kg/m2) Chronic obstructive pulmonary disease stade GOLD ≥2 Respiratory insufficiency due to any pneumopathy or neurologic disease. Cardiovascular disease as defined by either known coronary heart disease, history of ischemic or hemorrhagic stroke or cardiac insufficiency (ejection fraction <40%) Chronic kidney disease (GFR<60 ml/min) AND 2 distinct ABO group determination and Positive RT-PCR for SARS-CoV-2 on a respiratory tract sample of ≤ 3 days and days post symptom onset (DPOS) ≤ 3 days at inclusion or RT-PCR on a respiratory tract sample with CT value<20 or ascending kinetics at the time of perfusion and No additional oxygen requirement compared to baseline (WHO 8 ordinal scale < 4): asymptomatic, mild or moderate disease and Compatible ABO donor with neutralizing antibodies (NTAB) ≥1 :160 or equivalent according to predefined antibody commercial assays cut-offs (see Study procedures)  Exclusion criteria:  Seroconversion at the time of inclusion  Palliative care No signed informed consent History of previous transfusion-related Grade 3 adverse event according to Swissmedic definitions Disseminated intravascular coagulopathy (depending on specialist evaluation) Uncontrolled acute hypervolemia