BCG vaccine fine powder. Sometimes the powder is sealed with vacuum in a glass ampoule. Such a glass ampoule has to be opened slowly to prevent the airflow from blowing out the powder. Then the powder has to be diluted with saline water before injecting. The history of BCG is tied to that of smallpox. Jean Antoine Villemin first recognized bovine tuberculosis in 1854 and transmitted it, and Robert Koch first distinguished "Mycobacterium bovis" from "Mycobacterium tuberculosis". Following the success of vaccination in preventing smallpox, established during the 18th century, scientists thought to find a corollary in tuberculosis by drawing a parallel
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