Inclusion Criteria:  RT-PCR proven SARS-CoV-2 infection or computed tomography scan findings compatible with the COVID19 disease (bilateral multifocal ground-glass opacities ≥50%) Moderate to severe COVID-19 defined by PFR ratio of <200 SOFA score>4 Patients with vitamin D deficiency defined as 25 (OH)D level<20 ng/ml Age>18 years  Exclusion Criteria:  1. Vitamin D sufficient or already receiving vitamin D supplements 2. Active malignancy 3. Hypercalcemia, hyperparathyroidism 4. Chronic kidney disease (eGFR<30 ml/min) 5. Pregnant and lactating women 6. Patient on mechanical ventilation at ICU admission