Vitamin D is a secosteroid hormone which may have beneficial role in reducing COVID-19 adverse outcomes by first regulating the renin angiotensin system (RAS). Recent studies on animal in which acute respiratory distress syndrome (ARDS) was induced, showed that vitamin D lead to pulmonary permeability reduction by modulating RAS activity as well as the expression of the angiotensin-2 converting enzyme (ACE2). During COVID-19, downregulation of ACE2 leads to cytokine storm in the host, causing ARDS. In contrast, an experimental study conducted on mice in which ARDS was induced chemically, revealed that vitamin D admiration contributed to mRNA and ACE2 proteins levels improvement, ADRS milder symptoms as well as less lung damage.

Additionally, vitamin D had shown antiviral effects on several previous studies, that though to be exerted either by antimicrobial peptides induction which subsequently had direct antiviral action or through immunomodulatory and anti-inflammatory effects.

In addition, vitamin D stabilizes physical barriers which prevent viruses from reaching tissues susceptible to infection. Finally, previous studies demonstrated that hypovitaminosis D is accompanied by various comorbidities including diabetes mellitus, hypertension, chronic cardiovascular and respiratory diseases, and cancers, all medical conditions that are considered risk factors of COVID-19 infection deterioration and even high mortality rate.

The objective of this study is to evaluate whether supplementation with high-dose vitamin D improves the prognosis of patients diagnosed with COVID-19 compared to a standard dose of vitamin D.

Inclusion Criteria:

1. Age 18 to 65 years.
2. COVID-19 hospitalized patients with pneumonia confirmed by chest X-ray or CT scan.
3. RT-PCR Confirmed infection with COVID-19 or strongly suspected infection with pending confirmation studies.
4. Presence of acute respiratory distress syndrome (ARDS).
5. Having either peripheral capillary oxygen saturation (SpO2) ≤ 94% ambient air, or a partial oxygen pressure (PaO2) to fraction of inspired oxygen (FiO2) ratio ≤ 300 mmHg.

Exclusion Criteria:

1. Vitamin D supplementation in the previous month.
2. Contraindication for vitamin D supplementation: active granulomatosis (sarcoidosis, tuberculosis, lymphoma), history of calcic lithiasis, known hypervitaminosis D or hypercalcemia, known intolerance to vitamin D.
3. Organ failure requiring admission to a resuscitation or high dependency unit.
4. Pregnant women.
5. Participation in another simultaneous clinical trial.

All patients received the same background treatment for 5 days, following an Institutional protocol for standard of care: hydroxychloroquine 400 mg daily, lopinavir/ritonavir 400/100 mg twice daily or/and remdisivir 200 mg LD then 100 once daily as a maintenance dose and anti-coagulation prophylaxis with enoxaparin subcutaneously once a day if D-dimmer between 500-1000 or enoxaparin therapeutic subcutaneously twice daily if D-dimmer >1000.