Introduction: The emergence of SARS COV-2 and Coronavirus Disease 2019 (COVID-19) came without any known medication or treatment, thereby raising concerns for drug (therapeutics) research and development. Vitamin D is a potent immunomodulator with a proven protective effect against respiratory viral infections, and because of this, many studies have been carried out to evaluate the effects of vitamin D on COVID-19 infection, however, with varying conclusions.

Objective: To assess serum vitamin D levels and their correlation with IL-6 and other clinical characteristics among COVID-19 patients attended to at Mary Begg Health Services (MBHS).

Methods: This cross-sectional study was conducted among COVID-19 patients at MBHS. The study included 33 confirmed severe patients admitted to the intensive care unit, 45 patients with mild symptoms, and 45 healthy controls. The Kruskal–Wallis test was used to compare the median serum vitamin D levels among the three groups, and Spearman’s correlations were performed to assess the correlation between serum vitamin D, IL-6, and clinical characteristics of the patients.

Results: The majority of COVID-19 patients in this study had optimal levels of vitamin D 44/78 (56.4%), with vitamin D deficiency being observed in only 6/78 (7.7%). Vitamin D levels in the control group were not significantly different when compared to levels measured in severe and mild COVID-19 patients, median [IQR], 31.33 ng/ml [25.9-39.56] compared to 29.97 ng/ml [26.19-37.45] and 31.9 ng/ml [26.12-38.34], p = 0.916, respectively. Severe COVID-19 patients admitted to the intensive care unit were older and had median higher IL-6 levels (43.67 ± 11.86 years vs. 33.89 ± 13.38 years; p = 0.001 and 27.56 pg/ml [13.13-47.81] vs. 8.34 pg/ml [5.1-21.63]; p = 0.0003, respectively) than patients with mild disease. A significant negative correlation between vitamin D and IL-6 (r = - 0.42; p = 0.016) was found in severe COVID-19 patients.

Conclusion: A negative (inverse) correlation between serum vitamin D and IL-6 was found in this study. Therefore, patients with severe COVID-19 might benefit from vitamin D supplementation, which would help to downregulate the cytokine storm and hence reduced disease severity.