In light of these, it is not surprising that Jak and Jak3 inhibitor treatment during COVID-19 leads to adverse effects including respiratory tract infection, gastrointestinal events, and ulcerative colitis (Table 1) and which appears to be because of interference with the protective roles of mucosal epithelial functions of these Jaks in airways and gastrointestinal tracts (Kumar et al. 2021). This evidence concerns the gene JAK3 and COVID-19.