05 March 2007

Vaccine Milestones: Smallpox Is Dead

This case of smallpox was “made mild” by a vaccination, according to the caption on this undated photo.

By Elizabeth Fee, Ph.D.

Fee is the chief of the History of Medicine Division, National Library of Medicine, National Institutes of Health. She prepared these articles exclusively for eJournal USA.

The most dramatic vaccine success story in the more than 200-year history of vaccines is the eradication of smallpox in 1980. Smallpox was targeted for eradication for several reasons: It was transmitted from human to human and had no animal reservoir; an effective heat-resistant freeze-dried vaccine existed that could protect in a single dose; and practical diagnostic tools were available for the ready identification of smallpox infection.

The World Health Organization adopted the goal of eradicating smallpox in 1959, but progress was fairly slow until the Intensified Global Eradication program was launched in 1967. The strategy was to launch mass vaccination campaigns in each country, ensure the potency and stability of the vaccine, and cover at least 80 percent of the population. Those campaigns were followed by rigorous disease surveillance to detect outbreaks and target them with focused containment measures. Whenever an “index” case of smallpox was reported, all close contacts of the index case were vaccinated, and then all close contacts of those people would also be vaccinated. This method effectively isolated the index case and broke the chain of transmission.

The last case of smallpox was identified in Somalia in 1977. The search for smallpox cases lasted for another two years, and in 1980, the World Health Organization declared that “smallpox is dead!”

From the March 2007 eJournal USA, “Lifesaving Vaccines”