TYK2 and COVID-19: Overall, 13 significant loci were detected, with four of these loci being associated with increased susceptibility, including ABO locus, 3p21.31 genomic region (rs2271616 from SLC6A20 gene), and PPP1R15A. Nine positions are linked to increased likelihood of more severe symptoms and worse clinical outcome, including variants in genes TYK2, DPP9, and CXCR6 (Niemi et al., 2021; COVID-19 Host Genetics Initiative, 2020).