What is BCG?
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BCG (Bacille Calmette-Guérin) is a vaccine for TB that is given in many countries. In Canada, it is only given to a small group of high risk people. BCG does not provide very much protection from TB disease. It is often given at birth and used to protect infants and young children from very severe forms of TB disease. People who have been vaccinated with BCG can still become sick with TB disease. When BCG is given under one year old, in almost all people, it will no longer show in the body after 10 years.
BCG is not the cause of a positive TST if:
- BCG was given in infancy (under 1 year old), and the person is now aged 10 years or older.
- There is a high chance that a person has latent TB infection such as, a close contact of a case of TB disease, or lived in a community or country with high rates of TB. A high rate of TB is 30 or more people per 100,000.
- There is a high risk of TB infection progressing to TB disease.
BCG may be the cause of a positive TST if:
- BCG was given after 12 months of age AND
- There is no known exposure to TB disease or other risk factors AND
- The person is from a country with low rates of TB.