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Smallpox eradication
declared May 8, 1980 (last natural case 1977)· Event· Germs, drugs & genetics
Well documentedSolid records, physical evidence or scientific consensus.
A worldwide WHO vaccination campaign that ended smallpox, the first human disease ever eradicated.
See it on the Technology & Medicine map →How it works
In 1967 smallpox still caused an estimated 10 to 15 million cases a year in over 30 countries. The WHO campaign, led by American D. A. Henderson, shifted from vaccinating whole populations to 'surveillance and containment': find every case fast and vaccinate everyone around it. Freeze-dried vaccine and a cheap two-pronged needle helped. The last natural case was Ali Maow Maalin, a hospital cook in Somalia, in October 1977. Eradication was declared on May 8, 1980.
Why it mattered
Smallpox killed an estimated 300 million people in the 20th century alone. Its end saves lives and money every year and proved global cooperation, even across the Cold War, could work.
Think of it like
Like fighting a forest fire with firebreaks: rather than soaking the whole forest, crews clear a ring around each blaze.
How we know
WHO case records, the certification commission's reports, and the WHO's 1988 history 'Smallpox and Its Eradication'; the Soviet Union supplied much of the vaccine and the US much of the funding.
Still unknown or debated
The last known virus stocks are kept in two labs, in Atlanta and Koltsovo, Russia; whether to destroy them has been debated since the 1990s.
Connections (3)
▸Epidemics in the Americas included smallpox, the disease ended by Smallpox eradicationMostly agreed
The connection
Smallpox, which arrived with Spanish ships around 1518–1520, was among the deadliest of the Old World diseases that devastated Native American peoples, alongside measles, influenza and typhus. The same virus kept killing worldwide for another 450 years until the WHO campaign stopped it; the last natural case was in Somalia in 1977.
When and how
Hispaniola in 1518, then Mexico in 1520, where it struck Tenochtitlan during the Spanish conquest; eradicated by a WHO campaign run from 1967 to 1977.
How sure are we?
Spanish and Aztec accounts, including the Florentine Codex, describe the 1520 epidemic; eradication is documented by WHO case records and the 1980 declaration.
Debates and open questions
Death tolls in the Americas are debated, as is the share caused by smallpox versus other diseases, war, famine and enslavement.
▸Vaccination (Jenner's smallpox vaccine) made possible Smallpox eradicationWell documented
The connection
Jenner's 1796 discovery that cowpox protects against smallpox gave the world a safe vaccine. Over 170 years it was improved into a freeze-dried, heat-stable vaccine given with a cheap two-pronged needle. The WHO campaign used it to vaccinate everyone around each new case until the virus had nowhere left to spread.
When and how
Jenner in Berkeley, Gloucestershire, England, 1796; the WHO's Intensified Eradication Programme, 1967–1977, led by D. A. Henderson, across South America, Africa and South Asia.
How we know
WHO records document vaccine supply, case-finding and the last cases. Eradication worked because smallpox has no animal host and the vaccine gives long-lasting protection.
Debates and open questions
Oddly, the virus in modern vaccine, vaccinia, is not cowpox; genetic studies suggest it may descend from horsepox, and when the switch happened is unknown.
▸Smallpox eradication inspired a global eradication drive using Polio vaccines (Salk, Sabin)Well documented
The connection
Smallpox's defeat showed a disease could be wiped out worldwide. In 1988 the World Health Assembly launched the Global Polio Eradication Initiative, using the oral Sabin and injected Salk vaccines. Cases have fallen by over 99 percent from an estimated 350,000 in 1988, and wild polio now survives only in Pakistan and Afghanistan.
When and how
The World Health Assembly in Geneva, May 1988, with Rotary International, UNICEF and the US CDC; Rotary had begun its PolioPlus campaign in 1985.
How we know
The 1988 resolution cites smallpox's success, and smallpox veterans such as Ciro de Quadros went on to lead polio campaigns in the Americas.
Debates and open questions
Polio is harder: most infections show no symptoms, and the oral vaccine can rarely mutate and spread. Even D. A. Henderson doubted full eradication was achievable.