Protection against tuberculosis by Bacillus Calmette-Guérin (BCG) vaccination: A historical perspective.

Bacillus Calmette-Guérin (BCG) was developed exactly 100 years ago, and it is still the only licensed tuberculosis (TB) vaccine and the most frequently administered of all vaccines worldwide. Despite universal vaccination policies in TB-endemic settings, the burden of TB remains high. Although BCG protects against Mycobacterium tuberculosis infection and TB disease, the level of protection varies greatly between age groups and settings.