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 Then, in 1891, Louis Pasteur proposed that the terms vaccine and vaccination should be extended to include the new protective procedures being developed. Immunization refers to the use of all vaccines but also extends to the use of antitoxin, which contains preformed antibody such as to diphtheria or tetanus exotoxins. Inoculation is now more or less synonymous in nontechnical usage with injection and the like, and questions along the lines of "Have you had your flu injection/vaccination/inoculation/immunization?" should not cause confusion. The focus is on what is being given and why, not the literal meaning of the technique used. Inoculation