Gene expression analysis targeting markers associated with endothelial dysfunction, thrombosis, and inflammation revealed that serum from patients with severe COVID-19 significantly upregulated the expression of VCAM1 (1.43 ± 0.31-fold; p <0.01), F3 (1.59 ± 0.31-fold; p < 0.0001), PROCR (3.32 ± 0.65-fold; p < 0.0001), IL6 (1.72 ± 0.49-fold; p <0.01), and IL12A (2.26 ± 0.60-fold; p < 0.0001) in HUVECs after 60 min of stimulation (Figures 1, 2). Here, IL6 is linked to COVID-19.