I remember being vaccinated against smallpox as a child. We got the vaccine every two to three years to protect us during epidemics—and these were frequent enough. Thanks to a global immunization campaign by the World Health Organization (WHO), smallpox was declared eradicated in 1980; the last known case was in Somalia in 1977.
A global campaign to eradicate polio seems set to yield similar results. Last year, there were only eight reported cases worldwide, three of which were in Pakistan.