Vitamin D Deficiency and Receptor Polymorphisms as Risk Factors for COVID-19

Background: Early immune responses to COVID-19 can help eliminate the virus; therefore, strategies to improve the immune system have become important in disease prevention. Vitamin D plays a crucial role in the immune response to SARS-CoV-2 by increasing the expression of the vitamin D receptor. Objectives: This study investigated the impact of vitamin D deficiency, Fok 1, and Taq 1 Vitamin D Receptor (VDR) gene polymorphisms and comorbidities on the susceptibility to COVID-19. Methods: Fok1 and Taq1 polymorphisms were analyzed using the RT-PCR method, and vitamin D levels were measured using the chemiluminescence method. A total of 200 patients, 100 with COVID-19 and 100 without, provided blood samples for analysis. Results: The COVID-19 positive group had a significantly lower mean vitamin D level of 16.2 ± 11.3 ng/mL compared to the COVID-19 negative control group, 26.7 ± 15.9 ng/mL (P < 0.001). Individuals with a vitamin D level below 18.4 ng/mL had a 2.448 times higher risk of COVID-19 positivity (P < 0.001). There was no significant difference in the Fok1 and Taq1 gene polymorphisms between the two groups. (P = 0.548 and P = 0.098). The COVID-19 positive group had a significantly higher number of comorbid diseases with 40 (40%) compared to the negative group with 10 (10%) participants (P < 0.001). Conclusions: Levels of vitamin D above the cut-off value of 18.4 ng/mL were found to protect against COVID-19, while the presence of comorbid diseases was identified as a risk factor. However, no association was observed between the Fok1 and Taq1 polymorphisms and susceptibility to COVID-19.