Correlation analyses were performed with markers linked to thrombosis (D-dimer, fibrinogen, platelet counts, prothrombin time (PT), or TroponinT), and inflammation (white blood cell counts, lymphopenia with low lymphocyte counts, and C-reactive protein (CRP), interleukin-6 or procalcitonin levels) to identify associations between PAI-1 polymorphisms and thrombosis- or inflammation-associated clinical parameters in COVID-19 patients. The gene discussed is SERPINE1; the disease is lymphopenia.