Smallpox can be prevented in the vast majority of cases with a vaccine. Vaccination can be protective for up to several days after exposure to smallpox. Smallpox has been prevented through the effective Intensified Smallpox Eradication Programme, initiated by the World Health Organization.
On 26 July 1978, WHO announced the eradication of the smallpox strain Variola Minor. The more deadly strain, Variola Major, had been eradicated several years earlier, in 1975. While some other treatments available in the US today might treat smallpox infection, none have been fully (if at all) tested against smallpox.