Smallpox was most likely the first disease people tried to prevent by inoculating themselves[7][8] and was the first disease for which a vaccine was produced. The smallpox vaccine was designed in 1796 by the British physician Edward Jenner, although at least six people had used the same principles years earlier.[9] Louis Pasteur furthered the concept through his work in microbiology. The immunization was called vaccination because it was derived from a virus affecting cows (Latin: vacca—cow).[7][9] Smallpox was a contagious and deadly disease, causing the deaths of 20–60% of infected adults and over 80% of infected children.[10] When smallpox was finally eradicated in 1979, it had already killed an estimated 300–500 million people[11][12][13] in the 20th century.