Smallpox - Prevention

A person who has had smallpox can never have the disease again. This fact was known as far back in history as the tenth century. Medical workers in China, India, and the Americas made use of this information. They often tried to protect people from smallpox with a simple form of vaccination. First, they removed the liquid material from the rash of a person infected with smallpox. Then, they would make small scratches in the arm of the person to be vaccinated and place the liquid material from the infected person into the scratch.

This method had mixed results. Under the best circumstances, people who received this treatment developed a mild case of smallpox. They were then protected against the disease for the rest of their lives. However, the vaccinated person sometimes developed a full-blown case of smallpox. Instead of receiving protection from the disease, they would become ill from it.

In 1798 the English scientist Edward Jenner developed a variation on this procedure. He noticed that milkmaids sometimes caught a mild form of smallpox called cowpox. Cowpox was caused by a virus similar to, but less damaging than, the variola virus. Jenner used fluid from cowpox lesions to vaccinate people against smallpox. The cowpox fluid was much more likely to cause mild symptoms of the disease. But it still provided a person with protection against smallpox.

By the twentieth century a very effective smallpox vaccine was available. A vaccine (pronounced vak-SEEN) is a substance that causes the body's immune

system to build up resistance to a particular disease. Most young children in developed nations were routinely vaccinated against the disease and smallpox began to die out in some parts of the world. But it was still common in developing nations.

In 1967 WHO began a campaign to eliminate the variola virus completely. The organization watched carefully for outbreaks of smallpox throughout the world. When those outbreaks occurred, WHO workers were sent to the area where an epidemic was beginning. Everyone in the area was then vaccinated against the disease.

The program eventually worked. By 1980 WHO was able to announce that the disease no longer existed anywhere in the world. Today, samples of the variola virus exist in two research laboratories, one in Atlanta, Georgia, and one in Moscow, Russia. These samples are being saved for research purpose only. Some people worry that a relative of the variola virus may develop that can cause a smallpox-like infection. The variola samples might then be useful in developing a vaccine against the new infection.