Variolization was the first form of immunization used to transfer vesicle contents from smallpox sufferers into the scarified skin of healthy individuals as early as the 17th century.
In 1774, the English farmer Benjamin Jesty inoculated vesicle fluid from cowpox onto his wife and two sons and protected them against smallpox.
On May 14, 1796, Jenner injected 8-year-old James, son of his gardener Phipps, with material he had obtained from fresh cowpox lesions of a milker (Sarah Nelmes). To Jenner's relief, the boy subsequently developed only a slight fever. 6 weeks later, he exposed the boy to smallpox material. There was no smallpox infection. To Jenner's credit, he proved the correctness of his hypothesis that "cowpox protects against smallpox" (proof of concept). His investigations on other people led to the publication of "An Inquiry Into the Causes and Effects of the Variolae Vaccinae" in 1798 (1).
Vaccination skeptics already existed in his time, coupled with reports that people grew cow heads after vaccinations. As a late recognition of his achievements, the country doctor Jenner rose to become personal physician to King George IV in 1821. On October 26, 1979, the WHO declares smallpox eradicated. The smallpox virus only survives in high-security laboratories.