Vaccines

Edward Jenner's 1796 test on one boy, cowpox then a smallpox challenge that produced no infection, took nearly two centuries of further engineering to become the only disease eradication in human history.

1798

Albert Calmette and Camille Guerin spent thirteen years weakening a tuberculosis strain into the BCG vaccine, first given to a child in 1921, whose protection has since proved real but strikingly inconsistent from one country to the next.

A 1998 study of twelve children claiming a link between MMR vaccine and autism took thirteen years to be formally called fraud, and vaccination rates and measles cases moved in step the whole time.

In July 1885 Louis Pasteur gave an unlicensed, ethically fraught treatment to a bitten nine-year-old, having claimed far more animal testing than his own lab notebooks later showed he had actually done.