ABSTRACT
In the search for factors affecting incidence and lethality of the current COVID-19 pandemic, recent association studies explored the possible role of vitamin D deficiency. Altogether, these studies, in most cases based on cross-sectional analyses, could not yet provide a convincing demonstration of a cause-effect relationship. In this editorial, the authors describe the scientific evidence underlying a possible role of vitamin D in the prevention and development of the pandemic, considering its immunomodulatory role and antiviral effects. They conclude that further studies are needed to (1) better explore possible associations between vitamin D deficiency and COVID-19 morbidity and lethality, and (2) assess if compensating such deficiency could avoid or mitigate the worst manifestations of COVID-19. They highlight the need for public health campaigns to promote consumption of vitamin D-rich foods and proper sunlight exposition or, when this is not possible, controlled pharmaceutical supplementation, especially in countries with high prevalence of hypovitaminosis D.