Knowing that ordinary heated vaccine has no complete prophylactic action upon experimental typhoid fever, Besredka (1), in 1902, first used the so-called sensitized vaccine, which was made by combining the living typhoid bacilli with the useful constituents of immune serum. Later he investigated with Metchnikoff (2) its prophylactic value against experimental typhoid fever, and they found it effective and not dangerous to the human body. In 1914 Ichikawa, in Japan, experimented with the non-heated sero-vaccine upon typhoid fever patients with good results. In 1916, when the outbreak of cholera was at its height in Japan, the cholera sensitized vaccine was prepared by Shiga and his associates (3) and favorable results were obtained. Later Yabe published an article on cholera vaccine, its weak reaction and rapid development of antibodies, as compared with the ordinary vaccine.
We regret, however, that the sensitized vaccine in solution is not stable, and thus it cannot be kept for a long time in soluble form.