Four African countries have reported new cases of polio linked to the oral vaccine meant to protect against the disease.
Health numbers show more children are now being paralyzed by viruses from the vaccinations than wild polio viruses.
Last week, the World Health Organization, or WHO, and partners noted nine new polio cases caused by the oral vaccine in Nigeria, Congo, Central African Republic and Angola. Seven other African countries have similar cases, they said.
WHO and its partners also noted the problem in Asia. Of the two countries where polio remains widespread – Afghanistan and Pakistan – cases linked to the vaccine have been found in Pakistan.
In rare situations, the live virus in the oral vaccine can change into a form capable of causing polio infections. All the current cases that came from oral vaccines have been linked to a Type 2 virus contained in the vaccine. The Type 2 wild virus was eradicated years ago.
Polio, short for poliomyelitis, is a highly infectious disease. It spreads in water or food and usually affects children under the age of 5. About one in 200 infections leads to paralysis. Among those, a small percentage die when their breathing muscles no longer work.
Last week, donors promised $2.6 billion to fight polio as part of a plan aimed at eradicating the disease by the year 2000. The plan was launched in 1988. Since then, numerous targets for defeating the disease have been missed.
小儿麻痹症是小儿麻痹症的缩写，是一种高度传染性疾病。 它在水或食物中传播，通常影响5岁以下的儿童。每200个感染中就有1个导致麻痹。 其中，只有一小部分人会在呼吸肌肉不再工作时死亡。
To eradicate polio, more than 95 percent of a population needs to be vaccinated. For a long time, WHO and partners have depended on oral polio vaccines partly because production costs are low. In addition, the oral vaccines are easy to give, requiring only two drops per dose. Western countries use a more costly injectable polio vaccine that contains an inactivated virus, one that cannot cause polio.
WHO officials work with the Independent Monitoring Board, or IMB, to measure polio eradication. In a report this month, the IMB warned that polio virus from vaccines is "spreading uncontrolled in West Africa." The report said its spread raises important questions and problems for the eradication process.
要根除脊髓灰质炎，需要接种95％以上的人口。 长期以来，世卫组织及其合作伙伴一直依赖口服脊髓灰质炎疫苗，部分原因是生产成本低。 另外，口服疫苗易于给予，每剂仅需两滴。 西方国家使用昂贵的可注射脊髓灰质炎疫苗，其中包含一种不会引起脊髓灰质炎的灭活病毒。
世卫组织官员与独立监测委员会（IMB）合作，以根除脊髓灰质炎。 IMB在本月的一份报告中警告说，疫苗中的脊髓灰质炎病毒正在“在西非不受控制地传播”。 该报告说，其传播给根除过程带来了重要的问题。
Words in This Story：
oral– adj. of or relating to the mouth
paralyze– v. to make a person or animal unable to move or feel all of part of the body
eradicate– v. to eliminate or destroy something harmful
dose– n. the amount of a medicine, drug, or vitamin that is taken at one time
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