The DPP4 protein, together with ACE2, was found to be one of the binding sites of the SARS-CoV-2 virus, and the presence of the DPP4-DT Neanderthal-related haplotype in a heterozygous form was reported to double the appearance of severe COVID-19, while in a homozygous form, it correlated with a quadruple occurrence of severe disease [15, 16, 25, 26]. This evidence concerns the gene DPP4 and COVID-19.