With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: Dr. R. G. Ferguson, working at the Fort Qu'Appelle Sanatorium in Saskatchewan, was among the pioneers in developing the practice of vaccination against TB. In Canada, more than 600 children from residential schools were used as involuntary participants in BCG vaccine trials between 1933 and 1945. In 1928, BCG was adopted by the Health Committee of the League of Nations (predecessor to the World Health Organization (WHO)). Because of opposition, however, it only became widely used after World War II. From 1945 to 1948, relief organizations (International Tuberculosis Campaign or Joint Enterprises) vaccinated over eight million babies in eastern Europe and prevented the predicted typical increase of TB after a major war.
text_B: Did schools likely contact the vaccine manufacturers to signup for the BCG vaccine trials in Canada in 1935?
DON'T KNOW.