1798: Jenner self-publishes findings of cowpox vaccine efficacy
1853: Cowpox vaccine made mandatory in England (children)
For example, Thomas Jefferson injected slaves with the cowpox vaccine
to test the vaccine.
 Two-and-a-half decades later, Edward Jenner tested the cowpox vaccine
on his children and other children in the area where he resided.
Pancras, showing cowpox vaccine
Jenner's findings spread rapidly, but the cowpox vaccine
had to be transported from Europe to the rest of the world.
(Edward Jenner's cowpox vaccine
, the precursor of today's, was not invented until 1796.)
Ironically, the same year that Edward Jenner did his first experiments with the cowpox vaccine
(1796) was the year that Samuel Hahnemann, the founder of homeopathic medicine, performed his first experiments with homeopathy.