Immunisation gaps linked to China polio outbreak
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A group of Chinese scientists has linked a 2004 outbreak of polio in an impoverished Chinese province to gaps in China’s immunisation program, according to a study to be published in September.
In the article, to be published in The Journal of Infectious Diseases, the scientists recommend more widespread immunisation of China’s population as well as an end to the use of vaccines containing live but weakened strains of the polio virus.
“The outbreak ... highlights the need to carefully reconsider the risks associated with OPV (oral polio vaccine with live virus) use when formulating future polio immunization policies for China,” the researchers wrote in the article.
In the outbreak in southern Guizhou in mid-2004, six children, who had not been immunised, were left paralysed. Experts suspect they might have contracted the virus from other children who had been immunised with a live, but weakened form of the polio virus.
Oral polio vaccines containing live but weakened virus are used in many countries, partly because they are cheaper than their alternative, which contains a polio virus that is inactive.
But live-virus vaccine can cause sporadic cases of polio, either from the vaccine itself, or from the live virus in the vaccine getting out into the community - which may have been what happened in the Guizhou case.
Children who have been immunised shed the live virus in their stools and other children who might come into contact with the faeces could have picked up the virus and become infected.
Authorities say the Guizhou outbreak was brought under control following a province-wide immunisation programme in August 2004 that covered more than 90 percent of children under the age of five.
Guizhou had an immunization rate of only 72 percent when the researchers, led by Yu Jingjin at the Health Ministry’s Department of Disease Control, moved in to investigate in 2004.
The researchers warned in their study that the risk of polio outbreaks in China, although low, may increase in future because of a reduction in annual immunisation campaigns.
“These annual campaigns ... have decreased from 30 million to 60 million children per year during 1996-2003 to 12 million to 16 million children per year during 2004-2005,” they wrote.
“High routine immunization coverage, annual large-scale supplementary immunisation campaigns and sensitive and timely surveillance ... remain important government priorities to keep China polio-free.”
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