The Bacille Calmette-Guérin (BCG) Vaccine is a vaccine for tuberculosis disease, often given in countries where TB is common. It is not commonly given in the US, due to the lower risk of TB infection, and because it has variable effectiveness against adult pulmonary TB.
The vaccine has the potential to cause a false positive TB skin test reaction, and there is no way to distinguish a positive TB skin test reaction caused by BCG vaccination from a reaction caused by a true TB infection. The effect wanes after about five years from vaccination, but repeated skin testing may boost reactivity in vaccinated people. Therefore, if you have a new hire who has received the BCG vaccine in the past five years, it is recommended to use the blood test and not the skin test when conducting baseline TB testing. BCG vaccination does not induce positive results when the blood test is used.
It would be helpful to ask new hires whether they’ve received the BCG vaccine prior to their start dates to avoid false positives and possible duplication of testing.
