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 theory and others had found previously, inoculation was able to confer resistance to arguments that were not specifically mentioned in the inoculation message. Compton and Ivanov (2013) offer a comprehensive review of political inoculation scholarship and outline new directions for future work. Sample studies include: Pfau and some of his colleagues examined inoculation through the use of direct mail during the 1988 presidential campaign. The researchers were specifically interested in comparing inoculation and post hoc refutation. Post hoc refutation is another form of building resistance to arguments, however, instead of building resistance prior to future arguments, like inoculation, it attempts to