1. Body weight of less than 40 kg. 2. Severe or critical COVID-19 including at least one of: o Oxygen saturation (SpO2) ≤ 93 % on room air or on their usual level of oxygen supplementation in case of chronic oxygen use o Ratio of arterial oxygen partial pressure (PaO2 in millimeters of mercury) to fractional inspired oxygen (FiO2) < 300 (in case arterial blood sample was taken) o Respiratory rate ≥ 30/min or heart rate ≥ 125/min. Measure should be obtained at rest by study staff within 24 hours of start of treatment. o History of hospitalization for COVID-19 o Current or imminent need for hospitalization or immediate medical attention in the clinical opinion of the site investigator. Does not include patients hospitalized for isolation only. 3. Receipt of intraveneous immunoglobulin within 12 weeks prior to Visit number 2. 4. Receipt of COVID-19 convalescent plasma treatment at any time prior to Visit 2. 5. Receipt of any SARS-CoV-2 monoclonal antibody treatment at any time prior to Visit 2. 6. Receipt of SARS-CoV-2 vaccine at any time prior to Visit 2. 7. Receipt of an investigational product for COVID-19 within 5 half-lives prior to Visit 2. 8. Receipt of systemic steroids (e.g. prednisone, dexamethasone) within 4 weeks prior to Visit 2 unless used for chronic condition (see Section 4.2.2.1). 9. Patients who must or wish to continue the intake of restricted medications or any drug considered likely to interfere with the safe conduct of the trial. 10. Any co-morbidity requiring surgery within 7 days prior to study entry, or that is considered life threatening in the opinion of investigator within 30 days prior to study entry. 11. Have any serious concomitant systemic disease, condition or disorder that, in the opinion of the investigator, should preclude participation in this study. 12. Patients not expected to comply with the protocol requirements or not expected to complete the trial as scheduled (e.g. chronic alcohol or drug abuse or any other condition that, in the investigator’s opinion, makes the patient an unreliable trial participant). 13. Currently enrolled in any other type of medical research judged not to be compatible with this study. 14. Known allergy/sensitivity or any hypersensitivity to any of the components used in the formulation of the interventions. 15. Previous enrolment in this trial. Patients participating in Phase II are not eligible for Phase III. Re-screening is allowed once, for repeat of RT-qPCR or antigen SARS-CoV-2 test, if required. The test method used for initial screening (RT-qPCR or antigen) should be used for re-screening. 16. Women who are pregnant, nursing, or who plan to become pregnant while in the trial.

1. Body weight of less than 40 kg. 2. Severe or critical COVID-19 including at least one of: o Oxygen saturation (SpO2) ≤ 93 % on room air or on their usual level of oxygen supplementation in case of chronic oxygen use o Ratio of arterial oxygen partial pressure (PaO2 in millimeters of mercury) to fractional inspired oxygen (FiO2) < 300 (in case arterial blood sample was taken) o Respiratory rate ≥ 30/min or heart rate ≥ 125/min. Measure should be obtained at rest by study staff within 24 hours of start of treatment. o History of hospitalization for COVID-19 o Current or imminent need for hospitalization or immediate medical attention in the clinical opinion of the site investigator. Does not include patients hospitalized for isolation only. 3. Receipt of intraveneous immunoglobulin within 12 weeks prior to Visit number 2. 4. Receipt of COVID-19 convalescent plasma treatment at any time prior to Visit 2. 5. Receipt of any SARS-CoV-2 monoclonal antibody treatment at any time prior to Visit 2. 6. Receipt of SARS-CoV-2 vaccine at any time prior to Visit 2. 7. Receipt of an investigational product for COVID-19 within 5 half-lives prior to Visit 2. 8. Receipt of systemic steroids (e.g. prednisone, dexamethasone) within 4 weeks prior to Visit 2 unless used for chronic condition (see Section 4.2.2.1). 9. Patients who must or wish to continue the intake of restricted medications or any drug considered likely to interfere with the safe conduct of the trial. 10. Any co-morbidity requiring surgery within 7 days prior to study entry, or that is considered life threatening in the opinion of investigator within 30 days prior to study entry. 11. Have any serious concomitant systemic disease, condition or disorder that, in the opinion of the investigator, should preclude participation in this study. 12. Patients not expected to comply with the protocol requirements or not expected to complete the trial as scheduled (e.g. chronic alcohol or drug abuse or any other condition that, in the investigator’s opinion, makes the patient an unreliable trial participant). 13. Currently enrolled in any other type of medical research judged not to be compatible with this study. 14. Known allergy/sensitivity or any hypersensitivity to any of the components used in the formulation of the interventions. 15. Previous enrolment in this trial. Patients participating in Phase II are not eligible for Phase III. Re-screening is allowed once, for repeat of RT-qPCR or antigen SARS-CoV-2 test, if required. The test method used for initial screening (RT-qPCR or antigen) should be used for re-screening. 16. Women who are pregnant, nursing, or who plan to become pregnant while in the trial.