Working in Paris and India at the turn of the last century, Waldemar Mordecai Haffkine created the world's first vaccines for cholera and plague. Then an accidental mass poisoning derailed his life. In the spring of 1894, Waldemar Haffkine travelled to Calcutta in the Indian state of Bengal in search of cholera. Spring was cholera season in the city, and Haffkine was hopeful. He had arrived in India the previous March armed with what he believed was a vaccine for the disease, but he struggled all year to make progress testing his creation. From the moment of his arrival, Haffkine was met with scepticism and resistance from some of the British medical establishment and the Indian public. He was not a doctor but a zoologist. And he was a Russian Jew who had trained in Odessa and developed his skills in Paris, at a time when the world of international bacteriology was factional and prone to suspicion. Haffkine, who was 33 when he landed in India, also struggled with the practical side of testing his vaccine. His first iteration required two injections, separated by a week, and his team sometimes struggled to locate test subjects for the second prick. And despite the wide spread of cholera in India, finding it in sufficient concentration wasn't straightforward. Haffkine inoculated about 23,000 people that year in northern India, according to his own records, "but no cholera appeared in their midst to show whether the vaccine was of value or not". Then in March 1894, Haffkine got a break. He was invited to Calcutta by the medical officer there to help identify cholera bacilli in a water tank in one of the city's bustees - isolated villages on the outskirts of the city consisting of mud huts clustered around ponds or tanks and inhabited by the city's poor. The families living in these bustees drank collectively from the shared water sources, making them vulnerable to periodic outbreaks of cholera. To Haffkine, the bustees were an ideal proving ground for his nascent vaccine. In each household, he had a group of people living in identical conditions, equally exposed to cholera. If he could inoculate some of each family and leave some untreated, with enough participants he might finally produce some meaningful results. At the end of March, two people died of cholera in the Kattal Bagan bustee, signalling a new outbreak. Haffkine travelled to the bustee and inoculated 116 of the 200 or so inhabitants. Afterwards, his small team observed 10 further cases there, seven fatal - all among the uninoculated. The results were encouraging enough for the Calcutta health officer to fund a wider trial, but convincing people to be vaccinated was easier said than done. Years of top-down medical programmes by the British government had sowed distrust among the population, and to many the very concept of vaccination was still alien. Haffkine's solution was to work with a team of Indian doctors and assistants, rather than the British - Drs Chowdry, Ghose, Chatterjee, and Dutt, among others. And he had a new trick up his sleeve in the world of vaccinology: publicly injecting himself to prove he thought his preparation was safe. "What is remarkable, and is often lost in the story, is that after the initial resistance people began to queue in the slums in Calcutta for Haffkine's cholera vaccine, they queued for the whole day," said Professor Pratik Chakrabarti, the Chair in History of Science and Medicine at the University of Manchester. "He would spend hours and whole days in those slums working with Indian doctors. He would start vaccinating in the morning before people went to work, and continue after they came back in the evenings, sitting by an oil lamp in the slum." Haffkine's work in the Calcutta slums placed him among a select group of scientists who pioneered a profound and global shift in the way disease was understood and treated. But unlike Edward Jenner before him and Jonas Salk after, Haffkine's name never really entered the public imagination, either in India or in Europe. "Haffkine was the first person who brought that kind of laboratory medicine into a tropical country like India," Prof Chakrabarti said. "He was a Paris scientist who came to the slums of Calcutta. He has a very dramatic story."