The activation phenotype of T-cells showed that COVID-19 patients presented a higher proportion (median) of activated (HLA-DR+) CD4+ T cells: 6.2% (3.5–9.5) vs. 4.1% (3.5–5.5) (p = 0.023) and CD8+ T cells: 18% (9.1–26) vs. 9.5% (6–12) (p < 0.001, Table 2) compared to healthy controls. Here, CD4 is linked to COVID-19.