BCG vaccine 400 per 100,000 in that higher risk context). The age of the person and the frequency with which BCG is given has always varied from country to country. BCG is prepared from a strain of the attenuated (virulence-reduced) live bovine tuberculosis bacillus, "Mycobacterium bovis", that has lost its ability to cause disease in humans. Because the living bacilli evolve to make the best use of available nutrients, they become less well-adapted to human blood and can no longer induce disease when introduced into a human host. Still, they are similar enough to their wild ancestors to provide some degree of
Inoculation and the technique was known in India and China. The earliest hints of the practice of inoculation for smallpox in China come during the 10th century. A Song dynasty (960–1279) chancellor of China, Wang Dan (957–1017), lost his eldest son to smallpox and sought a means to spare the rest of his family from the disease, so he summoned physicians, wise men, and magicians from all across the empire to convene at the capital in Kaifeng and share ideas on how to cure patients of it until a divine man from Mount Emei carried out inoculation. However, the sinologist Joseph