Interestingly, BCG-induced immunity in patients with pre-existing immunity rather exhibited a shift towards IFN-γ single-positivity, which is consistent with cytokine profiles of antigen-specific T cells during reactivating infections such as cytomegalovirus, that is also characterised by a decrease in IFN-γ/IL-2 double-positivity and a concomitant shift towards IFN-γ single-positive cells [32]. Here, IL2 is linked to infection.