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 vaccine have never used it routinely are the United States and the Netherlands (in both countries, it is felt that having a reliable Mantoux test and therefore being able to accurately detect active disease is more beneficial to society than vaccinating against a condition that is now relatively rare there). Other names include "Vaccin Bilié de Calmette et Guérin vaccine" and "Bacille de Calmette et Guérin vaccine". Tentative evidence exists for a beneficial non-specific effect of BCG vaccination on overall mortality in low income countries, or for its reducing other health problems including sepsis and respiratory infections when given early, with