The smallpox vaccine is a vaccine that protects against smallpox, a highly contagious and deadly disease caused by the variola virus. Developed in the late 18th century by Edward Jenner, the vaccine uses a related virus called vaccinia to stimulate the immune system, providing immunity without causing the disease. Smallpox was declared eradicated in 1980 by the World Health Organization after a successful global vaccination campaign. Today, the smallpox vaccine is no longer given routinely, but it is stockpiled for use in case of a bioterrorism threat or accidental release of the virus.