Abstract
Despite the possible effects of Vitamin D (VD) in decreasing the risk of infections and mortality in some viral diseases, the role of therapeutic VD supplementation in individuals infected with COVID is still obscure. This article reviews the possible effects of VD on COVID-19 severity. MEDLINE–PubMed, EMBASE, and Cochran were searched following PRISMA guidelines. Some studies have reported that VD does not seem to augment the immunogenicity of seasonal vaccines, nor does it significantly reduce the incidence or duration of upper respiratory tract infection, although others have. The reason for not getting a positive or significant difference may be due to inadequate VD treatment levels, and VD may not be that important in immunized individuals with adaptive immunity. VD deficiency is most prevalent in the elderly, obese, men, ethnic minorities with darker skin, people with diabetes, hypertension, and in nursing homes or institutionalized. These are individuals that are at increased risk of severe consequences of COVID-19 such as acute respiratory distress syndrome with the need for mechanical ventilation and death. Perhaps supplementation of VD to adequate VD levels will improve the inflammatory reaction and modulate a faster patient recovery with decreased morbidity and mortality.