Background. SARS-CoV-2 virus is one of the largest RNA viruses, included in the coronavirus group, showing tropism to airway epithelial cells. SARS-CoV-2 causes an acute respiratory infectious disease, Covid-19. According to WHO reports, mortality due to Covid-19 is higher in the elderly and in those burdened with comorbidities such as diabetes, obstructive pulmonary disease, coronary artery disease, cancer, hypertension, hepatitis B, obesity or chronic kidney disease.
The aim of the study was to review the current literature on the influence and importance of vitamin D levels on the course of SARS-CoV-2 infection.
A systematic review of studies published from January 1, 2009 to June 31, 2021 has been performed. For this purpose, bibliographic databases such as PubMed and Scopus were searched. The following keywords and combinations were used: Covid-19, vitamin D, 25-hydroxy-vitamin D, vitamin D supplementation, SARS-CoV-2.
It has been shown that vitamin D plays an important role in the mechanisms of the innate immunity in the course of the acute respiratory infections. The overlapping factors of the severity of COVID-19 disease, vitamin D deficiency, and the prevalence of obesity, age scare, ethnicity, has led some researchers to hypothesize that vitamin D supplementation may be promising as a preventive or therapeutic measure for COVID-19.
A very important factor that has an immunomodulatory character is vitamin D, the adequate supplementation of which can be a preventive or therapeutic measure in case of SARS-CoV-2 infection, especially in elderly people, with obesity and other chronic diseases.

© Copyright by the National Institute of Public Health NIH – National Research Institute.