In 1967 smallpox killed some 2 million people. By 1979 the disease was officially declared to be extinct. This dramatic change was the result of a worldwide program of vaccination. Vaccines are substances that prevent the spread of a disease. They are used against a wide variety of diseases. Usually, vaccines are prepared from the same viruses or bacteria that cause the disease. How vaccines workWhen people are vaccinated, they are purposely infected with a bacteria or virus that causes a disease. Because the bacteria or virus has been killed or weakened first, it produces little if any sickness. But it does make the body's immune system produce proteins called antibodies that fight that particular disease. Therefore, if the body is then exposed to the actual disease it can fight it off and stay healthy. HistoryThe first vaccine was developed to fight smallpox. It was created in 1796 by an English surgeon named Edward Jenner. He saw that milkmaids rarely came down with smallpox even though they did get cowpox, a similar but much milder disease. So he tried an experiment: He took material from the cowpox sores of a young milkmaid and scratched it into the arm of a healthy 8-year-old boy. The boy became slightly ill with cowpox, as expected, but he quickly recovered. When Jenner later applied material from a smallpox sore to the same boy, it had no effect. Jenner concluded that cowpox infection provided immunity, or protection, from the later exposure to smallpox. He applied the name vaccine to the material from the cowpox sore, and he called the process vaccination. Both words are from the Latin vaccinus, meaning “from cows.” In about 1885 the French scientist Louis Pasteur took a slightly different approach in developing a vaccine against rabies, another terrible disease. He used a weakened form of the rabies virus itself to protect against a full-strength attack by the same virus. Pasteur also created a vaccine for anthrax. Vaccines today - In the 1950s American physician and researcher Jonas Salk developed a vaccine to combat …
Vaccination is used commonly for the prevention of many diseases. Vaccines for measles, mumps, and rubella are commonly given to children by injection—a shot with a needle. The original vaccine for polio, developed by Jonas Salk, was delivered in the same way, but the modern polio vaccine is given orally, or by mouth. Other vaccines are sprayed into the mouth or nose. Only the smallpox vaccine is still given through a scratch in the skin. Some vaccines need to be taken only once for lifelong protection. Others, such as the tetanus vaccine, require “booster” shots every so often. New medical technologies, including genetic engineering with DNA, hold great promise for the development and manufacture of vaccines. A single vaccine might one day protect people against many diseases, including some that are not currently preventable. |