Prevention of TB

The vaccine is made of living tuberculosis germs. They were first isolated in 1902 by Nocard from a cow that had tuberculosis. A sample of this germ was given to two French scientists who were trying to prepare a vaccine that would protect humans against tuberculosis. These men grew (cultured) bovine germs on a unique medium (food for the germ) that had not been tried previously. After replanting (subculturing) the germ several times they found that it was a little weaker than the one they started with originally; that is the germ was becoming attenuated (weakened). As a result of this observation they decided to subculture this organism every two weeks to see how weak they could make it.

They started this attenuation experiment in 1908. By 1919 they had so weakened the germ that it was not able to cause tuberculosis even in a guinea pig which is the animal most susceptible to tuberculosis. When they had the germ at this attenuated state they felt it was ready to be tried on human beings. In 1921 this vaccine was officially named BCG after the two French scientists, Calmette and Guerin who had produced it.

Soon after its availability in France, the vaccine went through thorough testing in Canada for safety and effectiveness. Canada had a pioneering role in the global acceptance of using BCG as protection against further spread of tuberculosis to uninfected people. In 1925 a BCG clinic was established in Montreal where they grew their own vaccine. In 1935 a vaccination program was started at an First Nations reserve by Dr. R. G. Ferguson and Dr. A. B. Simes. At the annual meeting of the Canadian Tuberculosis Association in 1947, endorsement was given to the extended use of BCG along the principles that BCG vaccine is an effective tool in the prevention and control of tuberculosis. The association recommended the use of BCG for protection of those unavoidably exposed to tuberculosis, whether in sanatoria or in their homes. Since then the procedure has been adopted throughout the world.

Canada has been a pioneer, not only in the study or in the clinical trials of B.C.G. but also in the routine use of this vaccine. As early as 1926 Montreal (Calmette had made known his results in humans in 1924) and in 1933 in Saskatchewan, important groups of individuals were B.C.G. vaccinated. Statistical studies made independently by two well-known Canadian investigators, Baudouin , (1926-1947) and Ferguson (1933-1947), established the safety and the value of B.C.G. vaccine and served as a basis for the development of the routine and systematic use of this vaccine in significantly large geographical areas of Canada. When considering the history of B.C.G. in Canada, one is impressed by the fact that, from the early beginning, our country has made and followed its own pattern of thought concerning the study and the use this weapon.

• Through the National Research Council, Canada was the first country in the world to support officially intensive and prolonged research on B.C.G.
• The Quebec and the Newfoundland provincial governments were the first in North America to encourage experimental and large clinical trials and establish officially in 1948, routine and systematic use of B.C.G.
• The Canadian Tuberculosis Association and its provincial branches have long recommended the practical use of B.C.G., although in provinces other than Quebec and Newfoundland the use of this vaccine had been more restricted and not officially introduced by the local governments as a systematic weapon in the program of preventive medicine.

Why would a person be vaccinated? Dr. Robert Koch, a German scientist, answered that question back in the latter part of the 19th century. He postulated and then proved that once a body is infected with tubercle bacillus, it was not so easily infected a second time. That is, once you have had the tuberculosis germ in your body, you are more resistant to a second infection. However, it is during that first infection that you develop tuberculosis if the natural body defenses cannot overcome the germ. This is where BCG comes into the picture. If we make your first infection with a tuberculosis germ that is unable to give you tuberculosis disease, then it is a harmless procedure and you are then able to resist more rapidly any other tuberculosis germ that you may come in contact with in your everyday life.

The vaccine is injected into the skin, over either the shoulder or hip, and the resulting reaction is not unlike that which occurred when people were vaccinated against small pox.