Global Eradication of Smallpox

Smallpox killed up to 30 percent of those it infected, about 3 in 10 on average, and left survivors scarred, sometimes blind. In 1967 the disease was endemic in 33 countries with 1.2 billion people, causing 10 to 15 million cases a year, fewer than 5 percent of them reported. Vaccination had been available since Edward Jenner's work in 1796, but mass campaigns alone had not reached everyone in endemic regions. The disease persisted in South Asia, sub-Saharan Africa, and parts of South America despite decades of vaccination programs.

The WHO's Intensified Smallpox Eradication Programme began in 1967 under Donald Henderson, an American epidemiologist from the CDC who took charge in October 1966. The program began with mass vaccination, but after Bill Foege, working in eastern Nigeria, showed that surveillance and containment worked far better, Henderson adopted it: find every case, isolate the patient, and vaccinate all contacts in a ring around the outbreak. This approach was more feasible in resource-limited settings than attempting population-wide coverage. Heat-stable freeze-dried vaccine and the bifurcated needle, invented by Benjamin Rubin of Wyeth Laboratories, cut training time and the amount of vaccine needed.

The campaign progressed continent by continent. Smallpox was gone from South America by 1971. In late 1975 a three-year-old Bangladeshi girl, Rahima Banu, became the last person to catch variola major naturally. The last cases were in the Horn of Africa, where variola minor, the less lethal strain, persisted. Ali Maow Maalin, a hospital cook in Merca, Somalia, developed the last naturally acquired case in October 1977. He survived. A two-year global surveillance period followed to confirm there were no hidden transmission chains.

The Global Commission for the Certification of Smallpox Eradication, scientists from 19 nations chaired by virologist Frank Fenner, certified eradication in December 1979, and the World Health Assembly declared it on May 8, 1980. The declaration ended routine smallpox vaccination in most countries. Live variola virus is kept in two authorized repositories, at the CDC in Atlanta and the VECTOR institute in Koltsovo, Russia, under WHO oversight. No other human infectious disease has been eradicated since.

The campaign led directly to the WHO Expanded Programme on Immunization and, through it, to the polio eradication program; more than 150,000 health workers took part, and in India alone field staff made more than a billion house visits. Henderson later directed the Office of Public Health Preparedness at the US Department of Health and Human Services and died on August 19, 2016.