This clinical trial will evaluate safety, immunogenicity, and prevention of Mtb infection, (measured by IGRA conversion) of H56:IC31 in remotely BCG vaccinated adolescents. A TB vaccination strategy incorporating H56:IC31 in adolescents or young adults, if found to prevent Mtb infection, would likely have a major impact on TB disease, TB transmission, and control of the epidemic. If vaccination with H56:IC31 is shown to prevent infection with Mtb in this proof of concept study in adolescents, additional larger scale studies examining the impact on TB disease in more diverse populations would be warranted.