Intravenous Immunoglobulin (IVIG, Bioven) Efficacy Assess for COVID-19 / SARS-CoV-2 Severe Pneumonia Complex Treatment

The screening stage: The patient or his legal representative must sign an informed consent. After signing the informed consent, the screening tests\&procedures are performed and the compliance with the inclusion / non-inclusion criteria is assessed. For patients who have been screened and meet the inclusion criteria and do not fall under the exclusion criteria, a blinded randomization procedure is provided. Randomization is performed by the IVRS method, according to the blinded-block patient's randomization table. The clinical stage of the trial: Begins after patient randomization. At the clinical stage, among other things, provides: * Determination of the individual dose of the study drug (in the study group) * Administration of the drug (in the study group) * Registration of adverse events * registration of information about taking antiviral drugs for the treatment of COVID-19; * registration of information on symptomatic therapy and administration of drugs for the treatment of comorbidities; * measurement of vital signs (blood pressure, heart rate, respiratory rate, body temperature); * Determination of SPO2 level * Determining the need for ventilation * Determining the need for intensive care * Assessment of compliance with the exclusion criteria Patients in the Control Group will receive therapy recommended by the COVID-19 coronavirus infection treatment protocol, depending on the severity of their condition according to the prescribing list, which will not include immunoglobulin preparations. Patients of the Study Group (IVIG) receive high-dose therapy with the study drug (Bioven, 10% solution for infusions produced by Biopharma Plasma LLC, Ukraine). The dose is calculated by body weight. Patients will also receive therapy recommended by the COVID-19 coronavirus infection treatment protocol, depending on the severity of their condition according to the prescribing list. Bioven administered intravenously, at an initial rate of 0.5 - 1.0 ml/kg body weight/hour for 30 minutes. In the absence of any undesirable side effects, the rate of administration can be gradually increased (recommended increase by 0.5 - 1.5 ml/kg body weight/hour every 10 minutes). According to results previously accomplished clinical studies, the maximum rate of Bioven administration is up to 8.5 ml/kg body weight/hour. Observation and completion stage: Begins and continues from the last administration of the study drug until the discharge of the patient from the hospital, but not less than 28 days from the confirmation of the diagnosis of pneumonia caused by coronavirus infection COVID-19. The following procedures are provided at the stage: * registration of information about taking antiviral drugs for the treatment of COVID-19; * registration of information on symptomatic therapy and administration of drugs for the treatment of comorbidities; * measurement of vital signs (blood pressure, heart rate, respiratory rate, body temperature); * determination of SPO2 level * registration of the results of the examination of the lungs by computed tomography (or radiography) * taking biomaterials for laboratory research: * general blood test (erythrocytes, hemoglobin, expanded leukocyte formula, platelets, etc.); * general analysis of urine; * biochemical analysis of blood; * state of the coagulation system * determination of inflammatory factors in the dynamics (CRP, ferritin, procalcitonin; TNF-α), IL-1-beta, IL-6, complement component C3 (C3), circulating immune complexes (CIC), etc.), * determination of IgG subclasses (G1, G2, G3, G4,); * Determining the need for ventilation * Determining the need for intensive care * Adverse reactions registration * Assessment of compliance with the exclusion criteria The patient's condition is assessed daily till discharge; and by schedule after discharge (if it happen earlier), during 28 days period after diagnosis of severe pneumonia caused by coronavirus infection COVID-19 In case of death of the patient - the date and cause of death are fixed. The results of the study are evaluated by endpoints.