BCG vaccine of 2004 the vaccine is given to about 100 million children per year globally. The main use of BCG is for vaccination against tuberculosis. BCG vaccine can be administered after birth intradermally. BCG vaccination can cause a false positive Mantoux test, although a very high-grade reading is usually due to active disease. The most controversial aspect of BCG is the variable efficacy found in different clinical trials, which appears to depend on geography. Trials conducted in the UK have consistently shown a protective effect of 60 to 80%, but those conducted elsewhere have shown no protective effect, and efficacy appears
BCG vaccine to fall the closer one gets to the equator. A 1994 systematic review found that BCG reduces the risk of getting TB by about 50%. There are differences in effectiveness, depending on region, due to factors such as genetic differences in the populations, changes in environment, exposure to other bacterial infections, and conditions in the lab where the vaccine is grown, including genetic differences between the strains being cultured and the choice of growth medium. A systematic review and meta analysis conducted in 2014 demonstrated that the BCG vaccine reduced infections by 19–27% and reduced progression to active TB by