August 16, 2006

Immunization gaps linked to China polio outbreak

HONG KONG (Reuters) - A group of Chinese scientists has
linked a 2004 outbreak of polio in an impoverished Chinese
province to gaps in China's Immunization 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
Immunization of China's population as well as an end to the use
of vaccines containing live but weakened strains of the polio

"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 immunized, were left paralyzed.
Experts suspect they might have contracted the virus from other
children who had been immunized 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

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 immunized shed the live virus in
their stools and other children who might come into contact
with the feces could have picked up the virus and become

Authorities say the Guizhou outbreak was brought under
control following a province-wide Immunization program 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 Immunization 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 Immunization campaigns and sensitive and timely
surveillance ... remain important government priorities to keep
China polio-free."