6 Children Infected with Polio from Oral Vaccine

[Guest guest]

Polio crippled six children in China after they were infected by a

mutated form of the virus excreted from children who were immunized,

illustrating the importance of full vaccination coverage even in

countries where the disease has been absent for years, a study says.

China has a vast polio vaccination program that reportedly covers

about 90 percent of the nation's children.

The six cases in 2004 in southern Guizhou, China, marked the country's

first outbreak in a decade. It also was the first time an outbreak

there was linked to the oral vaccine, which is made from a weakened

form of the polio virus, according to findings published Friday by

Chinese researchers in The Journal of Infectious Diseases.

Only about 60 children have been infected by vaccine-derived polio

virus in the past decade, according to the World Health Organization.

During that same period, more than 10 billion doses of the live oral

vaccine have been taken worldwide.

But despite its rarity, experts say the cases illustrate why countries

must remain vigilant in reaching all children in polio vaccination

drives — even if they haven't reported a case in years.

" You keep the course. You don't slack off, " said Walter Dowdle, senior

scientist at the U.S.-based Task Force for Child Survival and

Development, who co-authored an accompanying commentary in the

publication. " You have to be aware if you fall down on your

immunization levels, this could very well happen anywhere. "

The Chinese outbreak occurred in two villages in the country's poorest

province where vaccination levels were low. The six children, age 1

year to 7 years old, had not traveled outside the area, and were found

to be infected with a mutated form of the polio virus that had come

from the vaccine.

Only one of the children had been vaccinated.

Polio is spread through feces, which contaminates water and infects

those who are unvaccinated. It usually attacks young children,

targeting the nervous system. Most infected people never experience

symptoms, with only about one in 200 cases resulting in paralysis.

Usually, poor sanitation actually helps unvaccinated children who come

into contact with excretions from those who have been immunized. The

vaccine virus passively enters their systems and provides protection

from the disease.

" The downside is that in very, very rare instances, it does

genetically mutate and regain the ability to cause some paralysis, "

said Oliver Rosenbauer, spokesman for the WHO's polio eradication

initiative in Geneva.

Vaccine-derived polio virus has been documented in several countries

worldwide, including Haiti, Egypt, Philippines, Madagascar and Indonesia.

When the World Health Organization, UNICEF and the U.S. Centers for

Disease Control and Prevention joined forces with Rotary in a campaign

to eradicate polio in 1988, about half a million polio cases were

reported worldwide each year. Today, it's less than 1,000 cases.

" The benefits of the vaccine far outweigh any potential risks, "

Rosenbauer said.

Polio has been wiped out in much of the world, but remains endemic in

India, Pakistan, Afghanistan and Nigeria. Several other countries are

grappling with outbreaks from imported disease.

The Chinese study was led by Dr. Jingjin Yu of the Chinese Ministry of

Health, who did not return an e-mail from The Associated Press seeking

comment.

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