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 to back that idea up. There are also scholars on the other side who suggest that too much of a delay lessens the strengthening effect of inoculation. With this being said, it has been revealed that the effect of inoculation can still be significant weeks or even months after initial introduction or the treatment showing that it does produce somewhat long-lasting effects (Banas & Rains, 2010). Involvement is the final element of the inoculation process. Pfau, et al. (1997a) defined involvement as "the importance or salience of an attitude object for a receiver" and is “among the most important and