The relatively lower anosmia prevalence of the Omicron variant may be due to differences in tissue tropism, i.e., its specific preference for cathepsin-mediated endosomal entry over the surface in TMPRSS2-mediated membrane fusion; thus sparing the highly expressed TMPRSS2 olfactory epithelium from infection [47]. Here, TMPRSS2 is linked to Kallmann syndrome.