Task: Sentence Expansion
Input (English): Jenner thought that the pus in the blisters that milkmaids received from cowpox ( a disease similar to smallpox , but much less virulent ) protected them from smallpox .
Output (English): Noting the common observation that milkmaids were generally immune to smallpox , Jenner postulated that the pus in the blisters that milkmaids received from cowpox ( a disease similar to smallpox , but much less virulent ) protected them from smallpox .