Bacillus Calmette-Guérin, a vaccine giving protection against tuberculosis.(abbreviation for bacille Calmette-Guérin) bacillus injected as a vaccine to confer active immunity to tuberculosis (TB).<br /> BCG was developed by Albert Calmette and Camille Guérin in France 1921 from live bovine TB bacilli. These bacteria were bred in the laboratory over many generations until they became attenuated (weakened). Each inoculation contains just enough live, attenuated bacilli to provoke an immune response: the formation of specific antibodies. The recipient then has lifelong protection against TB.