CD27 and COVID-19: Later at D14–28, 16 cell subsets presented elevated global accuracy (AUC ≥ 0.8) to classify COVID-19 vs. HCs, with AUC = 1.0 registered for CD4+CD38+ and CD8+CD69+ and AUC = 0.9 observed for CD8+CD27+, CD3+CD107a+, CD4+T-bet+, CD8+CD107a+ and CD3+CD38+.