BCG Vaccine

All current strains of BCG (Bacille Calmette-Guerin) are derived from a strain developed by Leon Calmette and Camille Guerin at the Pasteur Institute, Lille, in the early 20th century (Sakula, 1983). Nocard had isolated a virulent M. bovis strain from a cow with tuberculous mastitis. This bovine strain, “Lait Nocard,” was sent to Calmette (Grange et al., 1983; Oettinger et al., 1999). He and Guerin had been working on bovine tubercle bacilli, that is, M. bovis. Between 1908 and 1921, 230 passages were completed (Corbel et al., 2004). There was an associated decrease in virulence of this strain in different animal species over this period (Sakula, 1983) and administration to humans as a vaccine began in 1921 (Sakula, 1983; Bryder, 1999). Even after this, for more than 10 years controversy raged over whether, in fact, the BCG strain was attenuated. Unfortunately, the original strain was lost during the First World War, and the exact process(es) that led to the attenuation of this M. bovis strain is uncertain (Grange et al., 1983).