Mozart and smallpox the imperial family were successful, and led to greater public acceptance for the procedure. Smallpox struck the Mozart family again in the next generation: Nannerl's eldest son Leopold and two of her stepchildren caught the disease during an outbreak in the Salzburg area in 1787. All three children survived. In 1796, the discovery of vaccination—the use of the related cowpox virus to immunize against smallpox—by Edward Jenner revolutionized the ability of medicine to deal with smallpox. Vaccination reached Vienna around 1800, when yet another local epidemic created impetus for its adoption. One of the doctors trained in the Vienna campaign,
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