PROS1 and COVID-19: These findings indicate: 1) low concentrations of S-protein appear sufficient to induce of IL-1β and IL-6 levels, but a higher concentration is required to induce IL-8 levels in HTR8, PMVECs and HEECs; 2) only higher concentration of rh-S-protein induces secretion of IL-6 and IL-8 levels in HTR8 and PMVECs; and 3) there is a clear inflammatory response to COVID-19 in vascular endothelial cells, potentially contributing to viral pathogenesis in pregnant women.