The in vitro model confirmed that patient plasma, with altered levels of sCD40-L and IFN-β proteins, has the capacity to alter endothelial function.<h4>Conclusions</h4>Six months post-ICU discharge, survivors of COVID-19-associated ARDS exhibited sustained elevation in endothelial dysfunction biomarkers, correlating with the severity of impaired gas exchange. Here, CD40LG is linked to COVID-19.