Convalescent Plasma for Patients With COVID-19: A Randomized, Single Blinded, Parallel, Controlled Clinical Study

Inclusion Criteria:Fulfilling all the following criteria 1. Olerder than 18. 2. Hospitalized participants with diagnosis of COVID 19 by Real Time - Polymerase Chain Reaction. 3. Severe cases according to the official guideline "Pneumonia Diagnosis and Treatment Scheme for Novel Coronavirus Infection (Trial Version 7)". 4. Sequential Organ Failure Assessment score (SOFA) \< 6. 5. Ability to understand and the willingness to sign a written informed consent document. Exclusion Criteria: 1. Female subjects who are pregnant or breastfeeding. 2. Patients with prior allergic reactions to transfusions. 3. Critical ill patients in intensive care units with requierment of Invasive Mechanical Venitlation. 4. Patients with surgical procedures in the last 30 days. 5. Patients with active treatment for cancer (Radiotherapy or Chemotherapy). 6. HIV diagnosed patients with viral failure (detectable viral load\> 1000 copies / ml persistent, two consecutive viral load measurements within a 3 month interval, with medication adherence between measurements after at least 6 months of starting a new regimen antiretrovirals). 7. Demonstrated coinfection that explains the patient's symptoms 8. End-stage chronic kidney disease (Glomerular Filtration Rate \<15 ml / min / 1.73 m2). 9. Child Pugh C stage liver cirrhosis. 10. High cardiac output diseases. 11. Autoimmune diseases or Immunoglobulin A nephropathy. 12. Patients have any condition that in the judgement of the Investigators would make the subject inappropriate for entry into this study.