Live attenuated vaccines for tuberculosis

Tuberculosis (TB) is a leading cause of infectious death worldwide. TB is caused by the bacterium Mycobacterium tuberculosis (Mtb) and transmission happens via inhalation of droplets and aerosols coughed by an individual with active disease. There are about 10 million cases of active TB annually, and it is estimated that approximately 2 billion people are latently infected. Although most latently infected individuals are not sick and do not transmit the disease, in about 5%–10% of these people the disease reactivates. TB kills about 1.5 million people each year and resistance to current treatments increases steadily. Prevention of TB via a vaccine is considered the optimal solution by the World Health Organization. Presently, the only licensed vaccine against TB, Bacillus Calmette-Guérin (BCG), prevents childhood versions of TB but affords low efficiency in the prevention and transmission of the disease in adults. Hence, an improved vaccine is urgently required to combat TB.