Tameris M, Mearns H, Penn-Nicholson A, et al. - Among adults and infants in an area where transmission of tuberculosis is very high, researchers evaluated the safety as and immunogenicity of the live-attenuated Mycobacterium tuberculosis vaccine candidate MTBVAC in this randomized, double-blind, BCG-controlled, dose-escalation trial. This investigation was conducted at the South African Tuberculosis Vaccine Initiative site near Cape Town, South Africa. Eligible participants were randomized to receive either BCG Vaccine SSI (5 × 10⁵ colony forming units [CFU] of Danish strain 1331 in 0.1 mL diluent) or MTBVAC (5 × 10⁵ CFU in 0.1 mL) intradermally in the deltoid region of the arm. Findings revealed the acceptable reactogenicity of MTBVAC, and its ability to induce a durable CD4 cell response in infants. The progression of MTBVAC into larger safety and efficacy trials was supported by the evidence of immunogenicity, which also confounds interpretation of tests for M. tuberculosis infection, emphasizing the necessity for stringent endpoint definition.