Similar to the CD8+ T cell activation pattern we observed, CD4+ T cells from COVID-19 patients showed a significant reduction in clusters with lower activation marker expression levels, including clusters 1 (p < 0.001), 2 (p < 0.001), and 8 (p = 0.002), and a significant increase in clusters with higher activation marker expression levels, including clusters 4, 5, 6, 9, and 10 (all p < 0.001). Here, CD4 is linked to COVID-19.