What if I had Bacillus Calmette-Guerin (BCG) vaccination for TB?

Bacillus Calmette-Guérin (BCG) is a vaccine for tuberculosis. It is often given to infants and young children in countries with high rates of tuberculosis. It protects children and babies from developing severe forms of tuberculosis, like meningitis or miliary TB. It is not used routinely in the United States. Your skin test may be positive because of BCG vaccination.

However, a positive skin test is most likely due to infection with TB bacteria if:

  • You recently spent time with a person who has active TB disease
  • You are from an area of the world where active TB is very common (Africa, Latin America, Asia, Eastern Europe and Russia)
  • You spend time where TB disease is common (homeless shelters, migrant farm camps, drug treatment centers, health care clinics. jails or prisons)
  • You were vaccinated more than 5-10 years ago
  • Your skin test is greater than 20 mm

Consider a blood test. Blood tests are not affected due to BCG - they will not give a false positive result due to BCG.