Vaccines疫苗
Vaccines: How they workThis is the VOA Special English Health Report.
Most vaccines are designed with the same goal in mind. That is, to help the body's own defense system prevent a disease by producing antibodies against it. Antibodies are disease-fighting proteins. The immune system produces them in reaction to viruses, bacteria and other invaders.
antibodies:抗体;
The vaccine tricks the body into thinking it has already successfully defeated the disease. To activate the immune system, vaccines commonly introduce the disease-causing virus or bacteria into the body. But they use weakened or killed versions.
weakened or killed versions:减毒或灭活疫苗Weakened viruses are used, for example, in vaccines against chickenpox, measles, mumps and rubella. To prevent polio, the Sabin vaccine uses a weakened form of the virus; the Salk vaccine uses a killed version.
chickenpox, measles, mumps and rubella:水痘,麻疹,流行性腮腺炎,风疹Experts say vaccines that use killed or inactivated virus can be safely given even to people with damaged immune systems.
Researchers may spend years working on a vaccine. They have still not succeeded against, for example, H.I.V., the virus that causes AIDS, or against malaria, but they are trying.
malaria:疟疾
And not all vaccines offer long-term protection. The tetanus vaccine is a good example. It offers protection for only about ten years. Then a person must be immunized again.
tetanus vaccine:破伤风疫苗
Some vaccines are made with animal material. For example, influenza vaccine is grown in chicken eggs. This can be a problem for people who are allergic to eggs. Also, the process is complex.
influenza vaccine :流感疫苗
But things could change in the future. A new study in the Journal of the American Medical Association suggests that flu vaccine could come from insect cells.
Researchers in the United States tested a flu vaccine made from caterpillar cells. The study involved four hundred sixty people. There were two versions of the vaccine, one stronger than the other.
flu vaccine =influenza vaccine :流感疫苗
The people were not told whether they were getting the vaccine or a substitute, a placebo. Here is what the scientists reported: Seven people in the placebo group caught the flu. So did two people who received the lower strength vaccine. But no one in the stronger vaccine group got the flu.
a placebo:安慰剂
Protein Sciences, a vaccine maker, paid for the study. The company plans to begin testing the experimental flu vaccine on a larger group in order to seek government approval.
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