To detect significant independent baseline biomarkers for COVID-19 severity, we aimed to perform in-depth immunophenotyping of major cell subsets present in human peripheral blood of COVID-19 patients and controls using a panel of ICPMs (PD1, TIM3, LAG3, TIGIT, and CD200R) and CD39 as markers for the purinergic signaling pathway. This evidence concerns the gene HAVCR2 and COVID-19.