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,
BCG disease outbreak in Finland in the 2000s been crimes committed relating to use of the BCG vaccine. BCG disease outbreak in Finland in the 2000s BCG disease is an adverse effect of the Bacillus Calmette-Guérin vaccine. The vaccine contains living "Mycobacterium bovis" BCG, and in BCG disease, the bacterium causes a disease in persons vaccinated. Between 2000 and 2006, several hundred children in Finland had serious adverse events from the vaccine, including osteitis and osteomyelitis, disseminated (usually fatal) BCG infection, arthritis, and lymph node abscesses. Four deaths were registered in the official adverse event register, and while in only two cases a clear causal link was considered