What is the Bacillus of Calmette-Guerin (BCG) vaccine?


In an attempt to prevent spread of tuberculosis (TB), particularly in young children, many countries with a higher incidence of tuberculosis than the United States vaccinate newborns (and sometimes adults as well) with BCG (Bacillus of Calmette-Guerin), an attenuated (weakened) live strain of a bacterium (Mycobacterium Bovis) similar to the tuberculosis. Because this vaccine is variable in its potency, its usefulness varies, and because it is not actually a vaccination with tuberculosis, but with another similar species, its effects are also usually short-lived. It is of proven effectiveness only for preventing the deadly complication of tuberculosis meningitis in young children. In the United States, it is generally agreed that a positive purified protein derivative (PPD) skin test found after two years from inoculation with BCG have passed should be considered an exposure to TB infection and treated as such.

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