(2022), who measured the extent of infection of cells in vitro by the Omicron variant (BA.1 sub-lineage) relative to other variants in different cell types, found that the Omicron pseudotyped virus entry was less efficient than the Wuhan 1 strain (B lineage) and Delta variant strains in Calu-3 and Caco-2 cell lines where the TMPRSS2 entry pathway is dominant for the Wuhan 1 strain. This evidence concerns the gene TMPRSS2 and infection.