Coronavirus disease (COVID-19) is an infectious disease caused by a new virus which causes respiratory illness. Older adults and people who have previous chronic medical conditions are at higher risk for more serious complications from COVID-19.Hypovitaminosis D is attributed to the increased risk of lung injury and acute respiratory distress syndrome (ARDS) as well as diabetes, Cardiovascular event and associated comorbidities, which are the main causes of severe clinical problem in COVID-19 patients. Considering the protective role of vitamin D through modulating the innate and adaptive immune system as well as inhibition of Renin Angiotensin System (RAS), vitamin D supplementation might boost the immune system of COVID-19 patients and reduce severity of the disease in vitamin D deficient individuals.

The Corona Virus Disease 2019 (COVID-19) outbreak is becoming pandemic with the highest mortality in people with associated comorbidities. These RNA viruses containing four structural proteins usually use spike protein to enter the host cell. It has been demonstrated that Angiotensin Converting Enzyme 2 (ACE2) ,as a part of renin-angiotensin-aldosterone system (RAAS), acts as a host receptor for the virus which is the main target of therapeutic approaches. However, medications acting on RAAS can lead to serious complications especially in people with diabetes and hypertension. To avoid this, other potential treatment modalities should be used in COVID-19 patients with associated comorbidities.

Results: A total of 6270 individuals were assessed (1615 severe and 4655 non-severe patients). The median age was 63 (95% CI: 49-74) and 47 (95% CI: 19-63) years in the severe and non-severe groups, respectively. Moreover, about 41% of patients had comorbidities. Severity was higher in patients with history of cerebrovascular disease: OR 4.85 (95% CI: 3.11-7.57). The odds of being in severe group increase by 4.81(95% CI: 3.43-6.74) for history of cardiovascular disease (CVD). This was 4.19 (95% CI: 2.84-6.19) for chronic lung disease and 3.18, 95% CI: 2.09-4.82 for cancer .The odds ratio of a diabetes and hypertension were 2.61 (95% CI: 2.02-3.3), and 2.37( 95% CI: 1.80-3.13) respectively.