Effects of Vitamin D on COVID-19 Infection and Prognosis: A Systematic Review

INTRODUCTION: Vitamin D status is related to risks of influenza and respiratory tract infections. Vitamin D has direct antiviral effects primarily against enveloped viruses, and coronavirus is an enveloped virus. The 2019 coronavirus disease had a high mortality rate and impacted the whole population of the planet, with severe acute respiratory syndrome the principal cause of death. Vitamin D can adequately modulate and regulate the immune and oxidative response to infection with COVID-19. The goal of this systematic review was thus to summarize and decide if there were a link between vitamin D status and COVID-19 infection and prognosis. METHODS: The protocol of this study is documented in the Prospero database and can be accessed with the protocol number CRD42020201283. PubMed and Google Scholar were used for a literature search from August 2020 to September 2020. We restricted the year of publication of reviewed articles to 2019–2020, and the selected language was English. Studies that used secondary data, feedback, or analysis of reviews were removed. To assess the standard of studies included, the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) method was used. RESULTS: Of the nine studies reviewed, seven (77.8%) showed that COVID-19 infection, prognosis, and mortality were correlated with vitamin D status. CONCLUSION: Most of the articles reviewed showed that blood vitamin D status can determine the risk of being infected with COVID-19, seriousness of COVID-19, and mortality from COVID-19. Therefore, maintaining appropriate levels of Vitamin D through supplementation or natural methods, eg, sunlight on the skin, is recommended for the public to be able to cope with the pandemic.