BCG (Bacille Calmette Guerin) is a freeze-dried, live but weakened (attenuated) form of Mycobacteria, the bacteria which causes tuberculosis (TB). BCG reduces the risk of TB meningitis and disseminated (miliary) TB in young children. Unfortunately it is less effective in preventing pulmonary TB, especially in malnourished children. It also gives less protection in adults.
In South Africa the Danish strain of BCG is being used.