Monitoring the Efficacy of a Probiotic Dietary Supplement SmartProbio C in Patients With Severe COVID-19 Infection

Inclusion Criteria: * The subject is willing and able to provide informed consent prior to any study procedure. * Age at the time of screening between 18 and 85 years inclusive. * Coronavirus (SARS-CoV-2) infection confirmed by polymerase chain reaction (PCR) or immunochromatographic detection of SARS CoV-2 specific antigens no more than three days prior to randomization. * COVID-19 symptoms lasting less than or equal to seven days, including. * Subject is currently hospitalized and requires medical care due to COVID-19 disease and was admitted at most two days prior to randomization. * Peripheral blood oxygen saturation \<94% on air (as measured by pulse oximetry or arterial blood sampling) at the time of inclusion in the trial. Exclusion Criteria: * Participation in any other clinical trial of an experimental treatment for COVID-19 disease. * Concomitant treatment of COVID-19 with other non-standard-of-care medications less than 24 hours prior to initiation of the study intervention dosing (excluding remdesivir, corticosteroids, casirivimab, imdevimab, or bamlanivimab). * Immunosuppressant treatment three months prior to hospital admission (excluding topical and inhaled corticosteroids or systemically administered corticosteroids at a dose equivalent to \<40 mg Prednisone) * Necessity of invasive pulmonary ventilation. * Patients with known primary or secondary immunodeficiency. * History of Crohn's disease or ulcerative colitis. * Abnormal screening laboratory results - laboratory abnormalities that, in the opinion of the investigator, will interfere with completion of participation in the clinical trial or will interfere with the results of the trial. * Participation in another clinical trial of a drug or medical device, or less than 30 days have elapsed since the completion of participation in another trial or use of the investigational drug or device. * Other probiotic supplementation. * Hypersensitivity to any ingredient of a product administered during a clinical trial. * Women who are pregnant or breastfeeding. * Patients with preterminal and terminal organ failure (COPD GOLD 3 and 4, CKD G4 and G5, NYHA 3 and 4). * Any condition that, in the opinion of the investigator, may compromise the patient's ability to provide informed consent and/or comply with all required study procedures.