Inclusion Criteria:

• 1. Hospitalized with COVID-19 respiratory symptoms and confirmation via COVID-19 SARS-CoV-2 RT-PCR testing.
• 2. Patient or their surrogate is willing and able to provide written informed consent and comply with all protocol requirements.
• 3. Diagnosis with Mild or Moderate Pneumonia not requiring mechanical ventilation: Patient must have at least one of the following features:
• i. Bilateral pneumonia present on chest radiograph or computed tomography ii. Partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2) on arterial blood gas showing: \>100mmHg and ≤ 300mmHg regardless of oxygen dose at time of testing.
• iii. Pulse oxygen saturation (SpO2) at rest ≤ 93% or any degree of hypoxia requiring supplemental oxygen
• 4. Patient agrees to storage of specimens for future testing.
• 5. Willingness to undergo mechanical ventilation for worsening

Exclusion Criteria:

• 1. Intubation with mechanical ventilation prior to study enrolment. High flow nasal cannula and non-invasive mechanical ventilation is allowed.
• 2. Pneumonia caused by bacteria, mycoplasma, chlamydia, legionella, fungi or other viruses
• 3. Obstructive pneumonia induced by lung cancer or other known causes
• 4. Significant comorbid illness likely to impact the outcome of COVID-19 including but not limited to active malignancy other than skin cancer.
• 5. Patients who are participating in other therapeutic clinical trials within 30 days of consent.
• 6. History of long-term use of immunosuppressive agents including prednisone dose \>5mg daily over the 30 days prior to enrollment.
• 7. History of severe chronic respiratory disease and requirement for long-term oxygen therapy
• 8. Undergoing hemodialysis or peritoneal dialysis
• 9. Estimated or actual rate of creatinine clearance \< 15 ml/min
• 10. History of moderate and severe liver disease (Child-Pugh score \>12)
• 11. Substance abuse sufficient that the patient is unlikely to comply with testing requirements.
• 12. History of deep venous thrombosis, pulmonary embolism, cerebral vascular disease within the last 3 years
• 13. Known HIV, hepatitis virus, or syphilis infection
• 14. Co-Infection of tuberculosis, influenza virus, adenovirus and other respiratory infection virus
• 15. Moribund patient not expected to survive \> 24hours
• 16. Allergy to diphenhydramine, or hydrocortisone
• 17. Any condition unsuitable for the study as determined by the investigators
• 18. Female subjects with positive pregnancy test, breastfeeding, or planning to become pregnant/breastfeed during the study period.
• 19. Receipt of experimental therapy for COVID-19 with the exception of convalescent plasma, dexamethasone or another corticosteroid, or remdesivir in an open label study.