TMPRSS2 and COVID-19: To determine whether miRNAs can modulate serum ACE2 and TMPRSS2 levels, this study investigated the predictive value of serum miR-200b-3p and miR-214-3p levels in correlating with the concentrations of ACE2 and TMPRSS2 in peripheral blood, respectively, in patients with severe and non-severe COVID-19.