Based on these premises, we aim to (i) evaluate the levels of serum E-selectin (sE-selectin) in COVID-19-hospitalized patients as marker of endothelial activation and (ii) to correlate the values of this biomarker with the severity of COVID-19, the in-hospital mortality rate and the occurrence of thrombotic events, adding new evidences to the comprehension of some aspects of SARS-CoV-2 infection pathogenesis. This evidence concerns the gene SELE and COVID-19.