Vitamin D supplementation has a protective effect, against the incidence of COVID-19 in RCT studies, OR 0.403, (95% IC 0.218, 0.747) In the RCTs performed on HCWs, the overall reduction in risk in the population supplemented with vitamin D was approximately 80% Against the incidence of COVID-19 in analytical studies OR = 0.592, (95% IC 0.476–0.736) Against the incidence of COVID-19 ICU admission OR 0.317, (95% IC 0.147–0.680). Our meta-analysis suggests a definitive and significant association between the protective role of vitamin D and COVID-19 incidence and ICU admission. Preventive Vitamin D Supplementation and Risk for COVID-19 Infection: A Systematic Review and Meta-Analysis https://www.mdpi.com/2072-6643/16/5/679 (28th Feb 2024) Vitamin D, crucial roles Bone homeostasis, muscle function, oncogenesis, immune response and metabolism. In the context of the COVID-19 Numerous researchers have tried to determine the role vitamin D in the immune response to the virus. Systematic review and meta-analysis, 15th May 2023 Preventive vitamin D supplementation, 16 publications N = 1,262,235 participants, A protective role in Incidence of COVID-19 Mortality Admission to intensive care units (ICUs). We calculated the Odds Ratios The assessment of potential bias and the evaluation of study quality will be conducted independently by two researchers. Extra information The majority of the effects of vitamin D are mediated by the VDR, which promotes the expression of genes containing specific DNA sequences and is expressed in almost all nucleated cells Approximately 3 percent of the human genome is under the control of 1,25-dihydroxyvitamin D Vitamin D has been observed to contribute to the synthesis of defensins, to be pivotal for enhancing the phagocytic activity, and to modulate the immune system response by regulating the inflammatory cascade