Numerous reports of vascular events after an initial recovery from COVID-19 form our impetus to investigate the impact of COVID-19 on vascular health of recovered patients . We found elevated levels of circulating endothelial cells (CECs), a biomarker of vascular injury, in COVID-19 convalescents compared to healthy controls . In particular, those with pre-existing conditions (e.g., hypertension, diabetes) had more pronounced endothelial activation hallmarks than non-COVID-19 patients with matched cardiovascular risk . Several proinflammatory and activated T lymphocyte-associated cytokines sustained from acute infection to recovery phase, which correlated positively with CEC measures, implicating cytokine-driven endothelial dysfunction . Notably, we found higher frequency of effector T cells in our COVID-19 convalescents compared to healthy controls . The activation markers detected on CECs mapped to counter receptors found primarily on cytotoxic CD8 + T cells, raising the possibility of cytotoxic effector cells targeting activated endothelial cells . Clinical trials in preventive therapy for post-COVID-19 vascular complications may be needed.