TMPRSS2 and viral infectious disease: Camostat inhibited the entry of wild type, Alpha, and Beta variants into Vero-TMPRSS2 cells; however, was unable to inhibit the entry of the Omicron variant into Vero-TMPRSS2 cells nor, as expected, stop viral infection of any of the variants when tested on HeLa-ACE2 cells lacking TMPRSS2 expression (Fig. 3A).