Bacille Calmette Guerin: An effective immunization against tuberculosis. Commonly abbreviated BCG, it is an attenuated (weakened) version of a bacterium called Mycobacterium bovis which is closely related to Mycobacterium tuberculosis, the agent responsible for tuberculosis.
Camille Guérin (1872-1961) and Albert Calmette (1863-1933) produced the BCG strain of the bacteria at the Pasteur Institute in Paris in 1921. Within a decade BCG was being given in France and many other countries. By 1928, BCG had been given to 116,000 infants in France alone. However, conflicting reports about its effectiveness delayed the use of the BCG vaccine in the United States until 1950.