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.