Is suboptimal circulating level of vitamin D a risk factor for the poor prognosis of COVID- 19? – A comparison of first and second waves in India

Background - Severe acute respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) affects every organ system, especially the lungs. Vitamin D has been shown to modulate both infections and autoimmune diseases. It maintains the balance between angiotensin-1 and angiotensin II, thereby preventing lung tissue damage. Hence arises the question - can adequate circulating vitamin D prevent or modulate SARS-CoV-2 infection? In the present study, we attempted to find the answer to this question in the Indian population. Methodology -The study duration was April 1, 2020 to April 30, 2021, including only those patients whose vitamin D levels were estimated. Mann-Whitney test was used to compare age, hospital stay, and total vitamin D levels between the two waves. The gender difference, vitamin D status, pre-existing comorbidities, COVID-19 severity, and mortality were calculated using the chi-square test. Results - On curating the data, vitamin D levels were found to be estimated in 179 COVID-19 positive patients. In the first wave, 48.2% of the patients were deficient in vitamin D levels, yet no statistical association was observed for patients’ demographics (age, sex, and comorbidities), COVID-19 severity, and mortality. Similar results were observed in the second wave. The correlation coefficient of IL-6 (r=-0.08), CRP (r = 0.033), and ferritin (r = 0.027) was not significantly associated with vitamin D levels. Conclusion - The Indian population is known to be deficient in vitamin D, yet this study showed an absence of vitamin D correlation with severity, morbidity or mortality of COVID-19. Further research into the immune-modulatory effect of vitamin D on disease susceptibility and progression in COVID-19 would be beneficial.