BCG vaccine for tuberculosis

British Columbia Specific Information

The BCG vaccine for tuberculosis (TB) can sometimes affect TB skin test results if it was given after 12 months of age or given more than once. However, this is uncommon if the vaccine was given when the person was a baby and they are now 10 years old or older and a positive TB skin test likely shows that they have TB infection.

A BCG vaccine is given to prevent tuberculosis (TB) infection. The vaccine contains bacteria called BCG (bacille Calmette-Guérin) that is closely related to the bacteria that cause TB.

The BCG vaccine is often given to people in countries where TB is common, such as South America, Africa, Asia, Eastern Europe, and Russia. But it is seldom used in North America because:

  • TB is not a widespread problem in North America.
  • The effectiveness of the vaccine varies. It is most effective at preventing TB from spreading outside of the lungs (extrapulmonary TB) in children.
  • The vaccine interferes with TB skin test results. People who get a BCG vaccination are likely to have TB skin test results that show they have a TB infection even when they aren't infected.