ABO and COVID-19: The first GWAS of COVID-19 clinical outcomes, which compared 1,980 patients with severe disease from Italy and Spain with population controls of unknown SARS-CoV-2 infection status, identified two genome-wide significant loci mapping to the 3p21.31 region, encompassing six genes (SLC6A26, LZTFL1, CXCR6, CCR1, CCR3, CCR9), and to the 9q34.2 region, which contains the ABO blood group locus [9].