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,
German retribution against Poles who helped Jews possible to organise public protests against deportations of the Jewish population. Calculations by Teresa Prekerowa show that only 1% to 2.5% of the adult Polish population was involved in helping Jews. However, the number of helpers was also very small in the countries of Western Europe - although hiding Jews there was associated with an incomparably lower risk. Assuming the percentage of the population of European countries, which in 1945 was made up of Jews who survived the Holocaust, Poland did not differ from the average in other occupied states. On the other hand, in the Netherlands, where few Jews