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,
Vaccination Act the parents or guardians were liable to a summary conviction and fine of 20"s". The Act also provided that any person who produced or attempted to inoculate another with smallpox could be imprisoned for a month. In 1871 another Act was passed appointing a Vaccination Officer, also authorising a defendant to appear in a court of law by any member of his family, or any other person authorised by him. This act also confirmed the principal of compulsion, which evidently sparked hostility and opposition to the practice. Made vaccination compulsory. Records of the reasoning for this are not widely available.