Background and Aim: Vitamin D has anti-viral, anti-inflammatory, and metabolic effects. The goal of this study was to evaluate the link between vitamin D level and COVID-19 incidence and to identify the result of short-term vitamin D deficiency correction in decrease the risk of COVID-19 infection. Patients and Methods: A prospective open-label controlled trial was carried out on 897 enrolled subjects who had contact with relatives infected by COVID-19 disease randomized into two arms according to baseline vitamin D level; the first arm of which 816 subjects (90.97% vitamin D deficiency) received 200,000 IU cholecalciferol/vitamin D3 every other day with a total of 3 doses, whereas the second arm, 81 subjects (9.03% normal vitamin D) didn't receive vitamin D supplementation. Serum calcium and serum vitamin D were measured at baseline and 2 weeks after treatment. CBC, ESR, CRP, ferritin, and D-dimer were performed in suspected cases. Results: Symptoms compatible with COVID-19 were 17.3% in the second arm and 16.4% in the first arm, Laboratory-confirmed diagnosis were 3.7% in the second arm and 5.4% in the first arm. Hospitalization was 1.2% in the second arm and 0.4% in the first arm. Deficient vitamin D levels increased the risk of symptoms compatible with COVID-19 disease by 1.66 folds.correlation was detected between P300 amplitude with IQ or language age (P > 0.05). Conclusion: Rapid correction of vitamin D deficiency decrease the risk of COVID-19 infection.