Tuberculosis: vaccines in the pipeline.

TB is presenting new challenges as a global health problem, especially with new threats of HIV coinfection and multidrug-resistant and extensively drug-resistant strains of Mycobacterium tuberculosis. The current TB vaccine, Mycobacterium bovis bacillus Calmette-Guerin (BCG), is the most widely used vaccine worldwide but its efficacy against pulmonary TB in adults in many high-burden countries is limited. Different vaccine strategies will probably be required for the various needs that exist within a population in which some individuals have been previously immunized with BCG, coinfected with HIV and/or latently infected with M. tuberculosis. In the last 15 years, new strategies to improve or replace BCG in the laboratory have led to several promising vaccine candidates that are actively being evaluated in human clinical trials. Some of these new vaccines may eventually be recommended for travelers to TB high-burden countries. This paper summarizes the progress of vaccine candidates in animal models to improve, replace or augment BCG vaccination.