The anti-vaccination movement can be traced back to the middle of the 19th century, when a U.K. government mandate for the smallpox vaccine met resistance from some residents of Leicester, England.
Smallpox was rampant throughout the 19th century and continued to ravage the world into the 20th. In the 1790's, an English doctor concluded that a small dose of the virus could provide immunity to it. In the 1850s, the British government made the smallpox vaccine mandatory, backed by fines and imprisonment.
At the time, the smallpox vaccine was not fine-tuned. While the early vaccine was accredited for falling infection rates, it also had severe side effects. An 1885 mass protest in Leicester highlighted the continuing resistance. In 1898, the government began allowing people to opt out.
The vaccine eradicated the disease in 1977, but an anti-vaccination movement has continued.