CD8A and COVID-19: Flow cytometry data for non-naïve CD8+ T cells in Mathew et al. [3] show generation of CD8+ T cells with larger abundances of the proteins CD38 and HLA-DR (CD38+HLA-DR+ cells) for some COVID-19 patients, forming an ‘elbow’ in the two dimensional PCD with CD38 and HLA-DR protein expressions (see S2 Fig).