Low plasma levels of the vitamin D metabolite 25-hydroxyvitamin D [25(OH)D] and the vitamin D receptor (VDR) gene single nucleotide polymorphisms (SNPs) have been associated with the body’s susceptibility to infectious diseases, including COVID-19. In this pilot retrospective study, representatives of the Kazakh population (central Kazakhstan) were divided into groups based on the test for IgM and IgG for coronavirus infection. We compared the 25(OH)D plasma levels and concluded that the COVID-19-positive group values (25.17 ng/mL ± 16.65) were statistically lower (p = 0.0114) compared to the COVID-19-negative ones (35.58 ng/mL ± 20.67). There was no association between age, gender and 25(OH)D concentration within the groups (p > 0.05). The genotyping of rs2228570 was performed using a TaqMan Real-Time PCR assay. Allele C predominated among the COVID-19-negative participants and significantly reduced the likelihood of coronavirus infection (p < 0.0001; OR = 0.0804; 95% CI 0.02357–0.2798). There were no statistically significant differences in the frequencies of the A, G and T alleles in the studied groups (p > 0.05). The GG genotype of rs2228570 was associated with a 4.131-fold increased likelihood of COVID-19 infection (p = 0.0288; χ² = 5.364; OR = 4.131; 95% CI 1.223–13.71). Comprehensive studies are required to determine whether low 25(OH)D plasma concentrations and genetic background represent a risk factor for COVID-19 infection.

This pilot study investigated the single nucleotide polymorphisms rs731236, rs1544410, and rs7975232 of the VDR gene using real-time ARMS-PCR in a cohort of 119 individuals of Kazakh ethnic group. Participants were stratified into COVID-19-positive (p-COVID-19; n = 88) and COVID-19-negative (no-COVID-19; n = 31) groups based on the detection of SARS-CoV-2-specific IgM and IgG antibodies by ELISA. The allelic and genotypic distributions of all three SNPs conformed to Hardy–Weinberg equilibrium. No statistically significant differences in allele or genotype frequencies were observed between the groups for rs731236, rs7975232, or rs1544410 (p > 0.05), indicating that these polymorphisms do not influence susceptibility to SARS-CoV-2 infection in the studied population. A borderline association was noted for the heterozygous CT genotype of rs1544410 (p = 0.0548), suggesting a potential protective effect (OR = 0.426; 95% Cl: 0.1816 – 0.9563). Despite the limited sample size, this is the first study to examine rs731236, rs1544410, and rs7975232 in relation to SARS-CoV-2 susceptibility within the Kazakh ethnic population, and one of the few to simultaneously analyze all four alleles of rs1544410.