Vaccination disease people tried to prevent by inoculation and was the first disease for which a vaccine was produced. The smallpox vaccine was invented in 1796 by English physician Edward Jenner and although at least six people had used the same principles years earlier he was the first to publish evidence that it was effective and to provide advice on its production. Louis Pasteur furthered the concept through his work in microbiology. The immunization was called "vaccination" because it was derived from a virus affecting cows ( 'cow'). Smallpox was a contagious and deadly disease, causing the deaths of 20–60% of
Vaccination policy de Janeiro, Brazil, following an urban renewal program that displaced many poor, a government program of mandatory smallpox vaccination triggered the Vaccine Revolt, several days of rioting with considerable property damage and a number of deaths. Compulsory vaccination is a difficult policy issue, requiring authorities to balance public health with individual liberty: "Vaccination is unique among de facto mandatory requirements in the modern era, requiring individuals to accept the injection of a medicine or medicinal agent into their bodies, and it has provoked a spirited opposition. This opposition began with the first vaccinations, has not ceased, and probably never will.