For 100 years, the Bacille Calmette-Guérin (BCG) vaccine has been used in tuberculosis (TB) prevention.  Although the vaccine is given to at least 100 million people annually, researchers have always questioned its effectiveness.  TB affects at least 10 million people a year across the world. A new study, The Lancet Global Health, by Boston University School of Public Health researchers, found the BCG vaccination at birth provides significant protection against TB, but only among children under five years old. View more