However, immunofluorescence microscopy showed that only a small portion of hESCs were infected and the infection rate of SARS-CoV-2 in H1 and H9 hESCs was 7.68‰ and 8.24‰, respectively (Table S2), consistent with the relatively low expression levels of ACE2 and TMPRSS2 in hESCs (Figure 1D). Here, TMPRSS2 is linked to infection.