The most advanced TB vaccine in clinical trials, MVA85A, induces a high frequency of polyfunctional CD4+ T cells in humans, however the vaccine was unable to boost BCG-induced protection in a Phase IIb trial.30 Further, these cells are detected after BCG vaccination in newborns, but there was no correlation between their frequency and protection against the TB in infants followed for 2 years after vaccination.31 A second major CD4+ T-cell subset observed after CysVac2 vaccination was composed of cells producing both IL-2 and TNF. Here, IL2 is linked to tuberculosis.