The story of smallpox prevention — and its eventual eradication through immunization — is a long and compelling one.
For centuries, it was known that people who survived smallpox became immune to it. For that reason, nearly every culture tried to induce immunity in healthy individuals. The Chinese used tubes to insert powdered smallpox scabs into their nostrils. In Turkey, pus from lesions was scratched into the skin.
Eventually these methods — collectively known as variolation — reached Europe and the New World. There, as elsewhere, variolation had varying degrees of success. Some people became immune, but others contracted the disease and died or became the source of a new epidemic. Still, by the early 1700s, “do-it-yourself” smallpox inoculation had become widespread.
In 1788, the scientist Edward Jenner inoculated a healthy, 8-year-old boy with cowpox — a disease caused by a virus that closely resembles variola. Cowpox’s natural hosts are small mammals such as wood mice, but the virus can spread to other animals, especially cattle. In cows, the disease causes lesions on the udders and teats that can infect humans who milk them. Although rare today, cowpox was widespread in 18th-century Europe, where it was common knowledge that milkmaids who had been infected with cowpox — which is generally mild — were then immune to the far more deadly disease, smallpox.
Jenner’s experiment was a success. His patient failed to contract smallpox, even when deliberately exposed to variola. By 1800, cowpox vaccinations (the word vaccine is from the Latin vacca, for cow) were commonplace, primarily because they caused fewer side effects and deaths than variolation with smallpox itself.
Smallpox vaccine that was used in the United States until 1972, when smallpox vaccinations were stopped, contained live vaccinia virus — a virus similar to cowpox and closely related to variola. Before 1972, most young children were vaccinated against smallpox, as were military recruits and many people traveling to other countries.
In 1967, the World Health Organization (WHO) launched a global immunization campaign to wipe out smallpox. At that time, 2 million to 3 million people died of smallpox every year. The WHO efforts were remarkably effective, and the last naturally occurring case of smallpox was reported in Somalia in 1977.
The global eradication of smallpox was verified and certified by a commission of prominent scientists in 1979 and endorsed by the World Health Assembly in 1980. In that year, smallpox vaccinations were discontinued worldwide.
The United States currently is increasing the supply of smallpox vaccine to have enough to vaccinate all Americans. In September 2002, the CDC (Centers for Disease Control and Prevention) released to health officials in all the states a contingency plan to quickly inoculate all Americans if the need should arise. Some experts have recommended “controlled vaccination.” This means that in the event of a smallpox outbreak, only people having close contact with infected persons would receive the vaccine.
Such a decision would not be undertaken lightly because the smallpox vaccine also has the small but real potential to cause serious harm. Experts in virology say the vaccinia vaccine causes a fatal complication in about 1 of every 1 million persons who receive it. That means that if the entire American population were to be vaccinated, 300 people would be expected to die of complications from the vaccine. Another 3,000 or so might develop painful sores and severe scars, while 600 others would likely have residual brain damage from encephalitis Inflammation of the brain. — a potentially fatal brain inflammation.
The current WHO guidelines also recommend against vaccination of entire populations, citing the risk of severe — and sometimes fatal — reactions to the vaccine. However, WHO officials emphasize that vaccination soon after exposure to the virus can prevent smallpox.