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 strengthen their original attitudes. It uses a threat on initial beliefs to trigger a person's desire to fight against the threat, ultimately reinforcing their attitude. William McGuire set out to conduct research “on ways of inducing resistance to persuasion, under the impression that while much experimental work was being done on factors that increased persuasive effectiveness, little was being done on ways of producing resistance to persuasion” (McGuire, 1964, p. 192). McGuire was motivated to study inoculation and persuasion as a result of the aftermath of the Korean War. Nine US prisoners of war, when given the opportunity, elected to