On chromosome 6, more specifically in the MHC class I and II regions (6p21.32, 6p21.33, 6p22.1), the evidence of association with COVID-19 comes from WGS, GWAS, functional (expression and affinity) studies, meta-analyses, and case–control studies, and this region contains several PID-related genes. Here, HLA-C is linked to pelvic inflammatory disease.