CD38 and COVID-19: Strikingly, in a recent study in COVID-19 patients, considerable proportions of peripheral CD4+ and CD8+ T cells co-expressed CD38 and HLA-DR, but those cells could not be re-activated with peptide pools of the S protein in vitro, supporting the notion of SARS-CoV-2 specific refractory T cells and/or different specificities (14).