Interestingly, genetic findings suggested that a risk haplotype in the extended promoter region of the DPP4 gene inherited from Neandertals increased the risk of critical illness in COVID-19 [8], and the rs3788979 DPP4 intron variant was associated with COVID-19 as well as with lower serum DPP4 protein concentration; however, the enzymatic activity was not reported [30]. This evidence concerns the gene DPP4 and COVID-19.