BCG vaccine bacilli that seemed less virulent, and changed the course of their research to see if repeated subculturing would produce a strain that was attenuated enough to be considered for use as a vaccine. The BCG strain was isolated after subculturing 239 times during 13 years from virulent strain on glycerine potato medium. The research continued throughout World War I until 1919, when the now avirulent bacilli were unable to cause tuberculosis disease in research animals. Calmette and Guerin transferred to the Paris Pasteur Institute in 1919. The BCG vaccine was first used in humans in 1921. Public acceptance was slow,
Inoculation to re-infection. In 1798, the English surgeon/scientist Edward Jenner published the results of his experiments and thus introduced the far superior and safer method of inoculation with cowpox virus, a mild infection that also induced immunity to smallpox. Jenner was not the first person to inoculate with cowpox nor the first to realize that infection with cowpox gave immunity to smallpox. However, he was the first to publish evidence that it was effective and to provide advice on its production. His efforts led to smallpox inoculation falling into disuse and eventually being banned in England in 1840. Inoculation The terms