BCG vaccine nesting birds and rusted electrical conduits. The resulting closure of the plant for over two years resulting in shortages of bladder cancer and tuberculosis vaccines. On October 29, 2014 Health Canada gave the permission for Sanofi to resume production of BCG. The global supply situation was analyzed in 2017 and concluded that the global supply is sufficient to meet forecasted BCG vaccine demand but risks for shortages remain mainly due to supply concentration. A weakened strain of bovine tuberculosis bacillus, "Mycobacterium bovis" is specially subcultured in a culture medium, usually Middlebrook 7H9. Some BCG vaccines are freeze dried and become
Inoculation specific immunity to the virus, while requiring more generations of the virus to reach levels of infection likely to kill the patient. The rising immunity terminates the infection. So the twofold effect is to ensure the less fatal form of the disease is the one caught, and to give the immune system the best start possible in combating it. Inoculation in the East was historically performed by blowing smallpox crusts into the nostril. In Britain, Europe and the American Colonies the preferred method was rubbing material from a smallpox pustule from a selected mild case ("Variola minor") into a scratch