CD27 and COVID-19: Although CD3+CD8+ effector memory cells mostly belonged to the subset of early effector cells as defined by their co‐expression of CD27 and CD28,40 COVID‐19 convalescent patients had a significantly lower frequency of this subset among their CD3+CD8+CD45RO+CCR7‐ effector memory T cells (65.6 ± 13.0 vs 69.7 ± 13.0%, P = .0129), which was at the expense of more differentiated CD3+CD8+ T effector memory subsets, that is, those co‐expressing CD27+CD28‐ and CD27‐CD28‐, respectively (Figure S5).