In particular, a GWAS study on Italian and Spanish patients identified two susceptible loci of severe COVID-19 including one locus on chromosome 3 with multiple genes included (SLC6A20, LZFTL1, CCR9, CXCR6, XCR1, FYCO1), and the other on chromosome 9 that defines the ABO blood types [7]. This evidence concerns the gene SLC6A20 and COVID-19.