The Bacille Calmette-Guerin Vaccine (BCG) is used to protect against the spread of tuberculosis, and therefore reduce the incidence of tuberculosis. BCG is a suspension of live tubercle bacilli (M. bovis) that have been attenuated, or made inactive, over a long period of time. This vaccine works as other vaccines do, to introduce the disease to your immune system. Although the attenuated bacteria can not cause the disease, the immune system picks up a "signature" of the disease, so that it will recognize related bacteria when encountered again. Your immune system will remember this signature and attack any cells it finds in the future, displaying the same signature. In this way, your body will immediately recognize and kill off active TB cells should you become infected later on.
Although the BCG vaccine was developed in France it has been used in Canada for more than half a century, and early BCG pioneers in Canada became world-famous for their work with this vaccine. At one time, the use of BCG in Canada was widespread, but now that the disease is far less common, BCG is only used for certain groups of people that are more likely to encounter the disease. These include:
BCG vaccination is not used for people that fit into one of the following categories:
Vaccination of pregnant women is preferably delayed until after delivery, although no harmful effects on the fetus have been observed.--taken from Canadian Tuberculosis Standards, 4th ed. 1996
To learn more about BCG, visit Prescription Drugs for Lung Diseases