More Polio Cases Now Caused by Oral Vaccine
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.
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.
I'm Alice Bryant.
1.oral vaccine 口服疫苗
Painful typhoid injections are a thing of the past, thanks to the introduction of an oral vaccine
2.change into 变成
You'd better change into some dry clothes.
3.linked to 与...有关
The authorities insist that the discussions must not be linked to any other issue
4.no longer 不再
They no longer had him as a friend.
5.For a long time, WHO and partners have depended on oral polio vaccines partly because production costs are low.
For a long time 长期以来
This account has remained unsettled for a long time.
I've been wanting to taste it for a long time.
6.For a long time, WHO and partners have depended on oral polio vaccines partly because production costs are low.
depended on 依赖
He depended on his writing for his income
They depended on animal husbandry for their livelihood.
上周，世界卫生组织(WTO)及其合作伙伴注意到尼日利亚、刚果、中非共和国和安哥拉出现了9例口服疫苗引起的脊髓灰质炎新病例 。他们说，其他七个非洲国家也有类似的情况 。
世卫组织及其合作伙伴还指出了亚洲的问题 。在脊髓灰质炎仍然广泛流行的两个国家——阿富汗和巴基斯坦，后者已经出现了与疫苗有关的病例 。
在罕见的情况下，口服疫苗中的活体病毒可转变为能够引发脊髓灰质炎感染的形式 。目前所有因口服疫苗导致的病例均与疫苗中含有的一种2型病毒有关 。2型野生病毒早在几年前就被消灭了 。
脊髓灰质炎是一种传染性极强的疾病 。这种病毒通过水或食物传播，通常影响的是5岁以下的儿童 。大约每200例感染中就有一例会导致瘫痪 。在这些人中，小部分人在呼吸肌肉停止工作时死亡 。
上周，捐助者承诺提供26亿美元用于抗击脊髓灰质炎，这是旨在到2000年根除该疾病的计划的一部分 。该计划始于1988年 。自那以后，许多攻克这一疾病的目标都没有实现 。
要根除脊髓灰质炎，超过95%的人口需要接种疫苗 。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较低 。此外，口服疫苗容易摄入，每剂只需两滴 。西方国家使用一种更昂贵的脊髓灰质炎疫苗，这种疫苗含有灭活病毒，这种病毒不会导致脊髓灰质炎 。
世卫组织官员与独立监测委员会(IMB)合作，以衡量根除脊髓灰质炎的情况 。独立监测委员会在本月的一份报告中警告称，疫苗中的脊髓灰质炎病毒正在非洲西部“失控地蔓延” 。报告指出，该疾病的传播给根除工作带来了重要的问题 。