Whereas severe COVID-19 vs. the control group featured a high percentage of CD45RO+CD45RA– CD8+ T cells, further analysis revealed that such a disease course was also associated with a high count of effector memory CD8+ T cells (CD27−CCR7−) that was parallel to a low level of transitional memory CD27+CCR7– CD8+ T cells [19]. The gene discussed is CD27; the disease is COVID-19.