But why think? Why not try the experiment?’ wrote the Scottish surgeon John Hunter to his pupil Edward Jenner in 1775. And so, on 14 May 1796, Jenner inoculated eight-year-old James Phipps with pus from a cowpox sore of a milkmaid, Sarah Nelmes. In Jenner’s experience, milkmaids who had contracted cowpox, a mild disease prevalent in cattle, were spared the grossly disfiguring and often-fatal outbreaks of smallpox. Gould this immunity be produced by arm-to-arm inoculation directly from a cowpox pustule, he wondered?
Phipps developed a mild fever and some blistering from which he recovered fully. Six weeks later Jenner inoculated him with smallpox. Phipps remained healthy. In 1798 Jenner announced the successful ‘vaccination’ of 23 patients against smallpox (vacca is Latin for cow). His method was instantly adopted throughout Europe, being much safer than inoculation with smallpox matter, a traditional Asian practice promoted by Lady Mary Wortley Montague, wife of the British consul in Constantinople, on her return to England early in the eighteenth century.
Meanwhile doctors debated whether smallpox and cowpox were two distinct diseases or the same disease with differing virulence. We now know they are distinct, but the idea that a mild version of a serious disease might confer immunity was to inspire Louis Pasteur half a century later while he was developing his germ theory of disease. He found that the microbes that cause chicken cholera could be weakened in culture, and that birds injected with these ‘attenuated’ bacteria were protected from the disease. He went on to produce attenuated anthrax bacilli and rabies virus, demonstrating their success as vaccines in a series of dramatic animal experiments in the early 1880s. The attenuation of infective disease agents remains a goal of vaccine development today.
Following a 14-year mass vaccination campaign, the World Health Organization announced in 1980 that smallpox had been eradicated once and for all.But there is smallpox viruses at lab in Georgia to use for future bio weapons.