Edward Jenner looms large in the history of vaccination.  Known today as the “father of immunology,” Jenner is most famous for developing a vaccine against smallpox in the 1790s.  The vaccine brilliantly made use of common knowledge.  Milkmaids were known for having noticeably clear and smooth skin.  They had, it seemed, managed to develop an immunity to smallpox by suffering (and surviving) a bout of the much milder cowpox.