Inclusion Criteria:  Male or female, ≥ 18 years old Diagnosed with COVID-19, as evaluated by laboratory diagnostic test or diagnosis based on radiological clinical findings  Baseline severity categorization of severe or critical COVID-19 infection per FDA Guidance for developing drugs and biological products for COVID-19 (February 2021)  Severe COVID-19  Symptoms suggestive of severe systemic illness with COVID-19, which include shortness of breath or respiratory distress Clinical signs indicative of severe systemic illness with COVID-19, such as respiratory rate ≥ 30 per minute, heart rate ≥ 125 per minute, SpO2 ≤ 93% on room air at sea level (SpO2 ≤ 90% at altitude) or PaO2/FiO2 < 300  Critical COVID-19  Oxygen delivered by high-flow nasal cannula (heated, humidified, oxygen delivered via reinforced cannula at flow rates >20 l/min with fraction oxygen ≥ 0.5) or Non-invasive mechanical or endotracheal mechanical ventilation Informed consent obtained from the patient or the patient's legal representative  Exclusion Criteria:  As a result of the medical review and screening investigation, the Principal Investigator considers the patient unfit for the study and/or progression to death is imminent and inevitable irrespective of the provision of treatments. Clinical diagnosis of respiratory failure (therapy not able to be administered in setting of resource limitation) Shock defined by systolic blood pressure <90 mm Hg, or diastolic blood pressure <60 mm Hg or requiring vasopressors. Multi-organ dysfunction/failure Patient has severe chronic obstructive or restrictive pulmonary disease (COPD) (as defined by prior pulmonary function tests), chronic renal failure, or significant liver abnormality (e.g., cirrhosis, transplant, etc.). Patient has chronic conditions requiring chemotherapy or immunosuppressive medication. A history of allergic reactions to human albumin (reaction to non-human albumin such as egg albumin is not an exclusion criterion) or ingredients in 5% human albumin (N-acetyltryptophan, sodium caprylate). Prolonged QT interval. Patient has known pregnancy or is currently breastfeeding. Patient planning to become pregnant, or father a child, during the treatment and follow-up period and/or is not willing to remain abstinent or use contraception. Participation in another clinical trial (not including treatments for COVID-19 as approved by the FDA through expanded access, emergency, or compassionate use), or participation in a trial such that enrollment in this study would fall within the time frame of the half-life of the other investigational product(s).