Smallpox was the first human disease eradicated worldwide through vaccination.
The World Health Organization certified smallpox eradication in 1980 after the last naturally occurring case was recorded in Somalia in 1977. The campaign succeeded because smallpox had no animal reservoir, infection usually produced recognizable illness, and vaccination provided strong protection.
The global program used surveillance and containment as well as mass vaccination. Health workers identified cases, traced contacts, and vaccinated people in surrounding communities. This targeted approach became especially important in the final stages, when cases were concentrated in relatively small areas.
Smallpox eradication is different from elimination. Elimination means stopping transmission in a particular region, while eradication means reducing worldwide natural transmission to zero. Laboratory samples of variola virus remain under international controls, but smallpox no longer circulates naturally among people.