CD38 and COVID-19: In this study, we aimed to evaluate total B and T cell count, T cell subgroups (CD4+ and CD8+ cells), expression of pan T cell markers, including CD2, CD3, CD5, CD7, and also some activated markers (CD38 and HLA‐DR) on T lymphocytes by multicolor flow cytometry, and examine its association with the disease severity and mortality in COVID‐19 patients.