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 (Banas & Rains, 2010, p. 285). Recent research has studied the presence and function of word-of-mouth communication, or post-inoculation talk (see Compton & Pfau, 2009), following exposure to inoculation messages (e.g., Ivanov et al., 2015). Delay is the next element that is necessary in the inoculation process. There has been much debate on whether there is a certain amount of time necessary between inoculation and further attacks on a persons' attitude that will be most effective in strengthening that person's attitude. McGuire (1961) suggested that delay was necessary strengthening a person's attitude and since then many scholars have found evidence