Waldemar Haffkine (1860-1930) conducted tests of his two-dose cholera vaccine in India beginning in 1893.
In his trials, he employed control and experimental groups, a relatively new practice for the time, and vaccinated more than 40,000 people. Though he was not always able to maintain rigorous controls, his methods would become useful models for future vaccine trials. His vaccine showed efficacy in many of the trial subgroups.
By mid-1896, Haffkine had concluded that the use of an initial attenuated vaccine was unnecessary, and so, as his trials continued, he tested only the second, more potent vaccine.