This is a Phase 1b/2a, double-blind, randomized, BCG-controlled, dose-escalation safety and immunogenicity study in 120 healthy adults with and without LTBI. All participants will have received previous BCG vaccination in infancy. The investigational product is MTBVAC at four dose levels: 5 x 10^3 CFU, 5 x 10^4 CFU, 5 x 10^5 CFU, and 5 x 10^6 CFU. The active control is BCG (5 x 10^5 CFU).