MODEL RELEASED. BCG vaccination. 4-week-old baby boy crying while a nurse gives him a BCG (Bacille Calmette-Guerin) vaccination. The needle is inserted intradermally to raise a blister. The vaccine injected is a live, weakened (attenuated) strain of bovine Mycobacterium bovis. This stimulates sensitivity to M. tuberculosis, the bacterium that causes tuberculosis (TB) in humans. The blister progresses to a papule or a benign ulcer within 6-12 weeks, leaving a scar. Most children receive the vaccine at around the age of 13. However, in cases where the risk is considered high, babies are given the vaccine soon after birth.