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 defensive, but weak enough to not actually change those preexisting ideas. This will hopefully make the receiver actively defensive and allow them to create arguments in favor of their preexisting thoughts. The more active the receiver becomes in his or her defense the more it will strengthen their own attitudes, beliefs, or opinions (McGuire, 1964). There are four basic key components to successful inoculation: threat, refutational preemption, delay, and involvement. The first is threat, which provides motivation to protect one's attitudes or beliefs (Pfau, 1997a). Threat is a product of the presence of counterarguments in an inoculation message and/or an