CD28 and COVID-19: Hence, we used a paired t-test analysis and examined whether participants DNAm-based estimates of CD8+ T cells, CD4+ T cells, natural killer (NK) cells, B cells, monocytes, granulocytes, plasmablasts, exhausted T cells (CD8+CD28-CD45RA-), CD8 naïve T cells, and CD4 naïve T cells significantly differed comparing pre- and post-COVID-19 time points.