Consistent with TMPRSS2-dependent plasma membrane fusion, IFITM1 was found to potently and significantly inhibit infection of early-lineage viruses (Wuhan-Hu-1 and VIC) and VOCs Alpha and Delta in both PV (Fig. 4 B–D) and live virus infections (Fig. 4 F–H). This evidence concerns the gene IFITM1 and infection.