Using CD28, KLRG1, CD57, TIGIT, PD‐1, and ICOS as biomarkers, higher frequencies of CD8+ and CD4+ T cells with mixed senescence/exhaustion phenotypes were observed in individuals with severe COVID‐19 when compared to individuals with mild disease and, for specific phenotypes, to individuals with moderate disease (Figure 3). This evidence concerns the gene ICOS and COVID-19.