Infectious Disease: Evolving Challenges to Human Health

Vaccination Can Eradicate Disease

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Smallpox was recognized in Egypt or India about 3,000 years ago. Uncontrolled epidemics ravaged the world for centuries, killing an estimated 300 million people during the 20th century alone. There has never been a cure, but today the world is free of circulating smallpox disease due to intensive vaccination programs. Some smallpox virus remains in repositories around the world. Since most people are susceptible, due to waning immunity, there is concern that someone could use smallpox as a weapon against society.

Discovery of Vaccination
Smallpox was the first disease ever controlled by vaccination. Edward Jenner observed that milkmaids who contracted cowpox did not get smallpox. Inoculating a person with cowpox caused a mild disease and the person did not become ill when later exposed to smallpox. This discovery led to the practice of vaccination to protect individuals from potentially deadly infections.

Drawing of Edward Jenner

Edward Jenner

Edward Jenner's observation that milkmaids who has contracted cowpox did not get smallpox lead him to discover the practice of vaccination against smallpox.

Global Eradication Effort

Vaccination against smallpox was so effective that new cases dropped from around 50 million during the 1950s to 10-15 million by 1967. In that year, the World Health Organization launched an intensified international effort to eradicate the virus, which still threatened 60% of the world’s population and claimed every fourth victim.

The End of Smallpox

In 1977, Ali Maalin of Somalia, the last person to naturally contract smallpox, recovered.

Photo of Ali Maalin

Ali Maalin

In 1978, Ali Maalin was the last person to naturally contract smallpox.

Eradication was possible because the smallpox virus depended on human-to-human transmission. There is no natural reservoir outside of people. By making enough people immune through vaccination, the virus ran out of susceptible people to infect. When the last infected people were identified and those around them were immunized, the virus had no place to go. The end of smallpox was certified worldwide in 1978.

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