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 (1995) posited that the use of inoculation strategies for these types of campaigns should be utilized to enhance the corporations' credibility and aide in maintaining the existing consumer attitude. This strategy should not be used to change consumer attitudes. Based on the analysis of previous research Burgoon et al. concluded issue/advocacy advertising is most effective for reinforcing support and avoid potential slippage in the attitudes of supporters. Based on previous publications they looked to test three hypotheses. The first was that issue/advocacy advertisements work to inoculate against counterattitudinal attacks. Next, issue/advocacy advertisements work to protect the source credibility. Lastly, conservatives