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 the sprouts", an idea of transplanting the disease which fit their conception of beansprouts in germination. Needham quotes an account from Zhang Yan's "Zhongdou xinshu" (種痘新書), or "New book on smallpox inoculation", written in 1741 during the Qing dynasty (1644–1912), which shows how the Chinese process had become refined up until that point: Two reports on the Chinese practice were received by the Royal Society in London in 1700; one by Dr. Martin Lister who received a report by an employee of the East India Company stationed in China and another by Clopton Havers. But no action was taken. According