CGB or the Calmette Guérin Bacillus is a micro-organism derived from the bovine tuberculosis bacillus (Mycobacterium bovis). Albert Calmette, a physician and biologist and Camille Guérin (a veterinary practitioner and biologist) obtained a strain that was not virulent to human beings from a culture in specific medium and selection during the years after 1908.
The first CBG vaccine against tuberculosis was used in a child on the 18 July 1921. In 1924, the government approved vaccination of newborn babies with CBG. In France at present (2007), vaccination is mandatory for children. This may be questioned at some point in the future.
The CBG vaccination is based on the principle of superinfection. The micro-organism is injected alive and in surviving in the human body, in order to maintains the protective reaction. In general, CBG becomes established in a lymph node. It cannot survive the injection or disappear over time. The action of the vaccine is then cancelled out.
A few side effects are sometimes seen (scarring, erythema, persistent skin ulceration, inflammation of the axillary lymph node on the side of the vaccinated arm).
Its efficacy has been questioned. It is at best relatively limited. Studies on this issue differ significantly. The most serious forms of tuberculosis in children are the best protected.
As tuberculosis is related to hygiene conditions, the incidence of the disease has become very low in developed countries and the benefit of routine vaccination is less apparent.