Ellen Druger, age 13, of Baltimore, Md., for her question:
HOW DOES MEASLES VACCINE WORK?
Millions of children since 1963 have received injections of a vaccine to prevent measles. In that year, an American bacteriologist named John Enders developed the vaccine that has reduced the number of U.S. measles cases by more than 95 percent.
Live measles virus that has been weakened by a long period of growth in animal cells in a test tube are contained in measles vaccine. When injected into a person's body, the weakened virus produces a mild form of the condition that results in measles.
In most people, the mild condition produced by the vaccine doesn't bring any of the measles symptoms. But the body reacts to the weakened virus just as it would react to an ordinary virus. That is, it produces antibodies that fight the virus and later provide immunity to measles.
Scientists do not know how long the immunity lasts, but it definitely continues for many years. It may even last for life.
Before the development of the measles vaccine, gamma globulin treatment was the most common method of trying to prevent the disease. In this treatment, a doctor injected gamma globulin, a part of the blood. The gamma globulin that is used comes from people who have had measles, and so it contains antibodies.
The treatment was used for persons who had come in contact with the disease but had not yet developed any symptoms. It often prevented measles or made the disease less severe.
Doctors still use gamma globulin for persons who have come in contact with measles but have never received the vaccine. They use it instead of the vaccine because the vaccine cannot stop measles from developing in someone who has the virus.
A virus causes measles. People who have the disease spread the virus by coughing and sneezing. The first symptoms appear about 10 days after the virus enters a person's body.
No drug exists to cure measles after it develops. Patients should be kept comfortable while the disease runs its course.
In most cases, a person can have measles only once. The body produces antibodies, which are substances that fight infection, during the disease. These antibodies normally provide lifelong immunity or protection from later attacks.
Measles occur chiefly in children, but adults can catch it, too. Although the disease kills many undernourished children in poor countries, very few people in Canada or the United States die of measles.
The medical name for measles is rubeola. German measles, known medically as rubella, is a different disease with similar symptoms.
Some people who are weakened by measles suffer complications. Such complications include infections of the lungs and middle ear. The measles virus can also harm the brain, but fortunately this rarely happens.