Mycobacterium bovis Bacille Calmette-Guerin (BCG) is one of the most widely used vaccines. Modern techniques in genome manipulation allow the construction of recombinant (r)-BCG strains that can be employed as highly immunogenic vaccines against tuberculosis (TB) with an enhanced safety profile. In addition, the development of novel procedures to cultivate BCG will allow the large-scale production of future BCG-based vaccines.