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What if I Have Been Vaccinated

with BCG?

BCG is a vaccine for TB. This vaccine is not widely used in the United States, but it is often given to infants and small children in other countries where TB is common. BCG vaccine does not always protect people from TB.

If you were vaccinated with BCG, you may have a positive reaction to a TB skin test. This reaction may be due to the BCG vaccine itself or to a real TB infection. But your positive reaction probably means that you have TB infection if :

  • your skin test reaction is large
  • you were vaccinated many years ago (because the BCG reaction gets smaller over time)
  • you have ever spent time with a person with infectious TB
  • someone in your family has had TB
  • you are from a country where TB disease is very common (most countries in Latin America and the Caribbean, Africa, and Asia, except for Japan)

The Quantiferon-TB Gold Test detects true LTBI and does not react to BCG.