On Jan. 10, 1897, Russian physician Waldemar M. W. Haffkine, who trained with Louis Pasteur in Paris, tested a vaccine he had created to combat a bubonic plague epidemic in Bombay, on himself.

Haffkine had chosen a fluid medium for the growth of the plague bacilli to allow extracellular toxins to accumulate. He reasoned that a vaccine containing both killed bacilli and their extracellular toxin would be more effective both in protecting against infection and in combating the disease in those already infected, a result not observed with the anticholera vaccine.

Early results from trials where accurate statistics had been kept showed that not only was the rate of attack diminished in the inoculated but also fewer of the attacks were fatal; the Commission accepted this.