The development of the first vaccine for smallpox is credited to Edward Jenner. In 1796, Jenner discovered that cowpox infection conferred immunity to smallpox, which was a devastating disease at the time. His pioneering method involved inoculating individuals with cowpox to prevent smallpox infection, laying the groundwork for the field of immunology. Jenner's work not only drastically reduced smallpox mortality rates but also set a precedent for vaccination practices, significantly influencing public health policies throughout history.