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
Mozart and smallpox reached European countries. Inoculation was not the same as the vaccination which later succeeded in eradicating the disease; rather, an inoculated person was treated with live smallpox virus, taken from pustules of the mildest variety of smallpox that could be found. Inoculation offered immunity to smallpox, but the procedure carried a definite risk that the inoculated person could die from smallpox as a result. Thus, many parents felt that they would rather do nothing, risking future smallpox arriving at random, rather than carry out a deliberate act that might well kill their children immediately. As Mozart biographer Ruth Halliwell points