BCG vaccine extensively used even in countries where efficacy against pulmonary tuberculosis is negligible. A number of possible reasons for the variable efficacy of BCG in different countries have been proposed. None have been proven, some have been disproved, and none can explain the lack of efficacy in both low-TB burden countries (US) and high-TB burden countries (India). The reasons for variable efficacy have been discussed at length in a WHO document on BCG. BCG has protective effects against some non-tuberculosis mycobacteria. BCG has been one of the most successful immunotherapies. BCG vaccine has been the "standard of care for patients with
Inoculation a 20% incidence of severe scarring), many parents felt that the benefits of inoculation outweighed the risks and so inoculated their children. Two forms of the disease of smallpox were recognised, now known to be due to two strains of the Variola virus. Those contracting "Variola minor" had a greatly reduced risk of death – 1–2% – compared to those contracting "Variola major" with 30% mortality. Infection via inhaled viral particles in droplets spread the infection more widely than the deliberate infection through a small skin wound. The smaller, localised infection is adequate to stimulate the immune system to produce