A BCG vaccine is given to prevent tuberculosis (TB) infection. The vaccine contains bacteria called BCG (bacille Calmette-Guérin) that is closely related to the bacteria that cause TB.
The BCG vaccine is often given to people in countries where TB is common, such as South America, Africa, Asia, Eastern Europe, and Russia. But it is seldom used in the United States because:
WebMD Medical Reference from Healthwise