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Polio Outbreak in Syria Sparked by Vaccine, Health Officials Say

polio2The World Health Organization said Tuesday that an outbreak of vaccine-related polio cases in Syria has expanded, with 17 children so far paralyzed by the vaccine viruses.

Two weeks ago, there were only two cases. Test results are pending for another 27 individuals, although some of them may turn out not to be polio cases.

One of the newly confirmed cases is in Raqqa, the self-proclaimed capital of the Islamic State — a factor that could add layers of complexity to an already difficult situation. The other 16 are in Mayadeen district in the Deir-Ez-Zor governorate of eastern Syria.

“The Raqqa case is further being investigated, including to more clearly assess whether there is local circulation in Raqqa as well, or [if this is] an isolated importation from Mayadeen,” Michel Zaffran, director of polio for the WHO, said in an email. “We are also looking at the options for extending the response to Raqqa which … will be more complicated given the current situation.”

Related: Massive polio vaccination campaign targets
over 116 million children in Africa

Planning is underway to conduct two special rounds of immunization. The first round is expected to begin no later than July 8 and will use a special oral vaccine that targets type 2 polio. The goal is to vaccinate 328,000 children under the age of 5.

A second round, which will use injectable polio vaccine — the type used in the United States — will aim to vaccinate 114,500 children between the ages of 2 months and 24 months. Zaffran said while speed is of the essence, planning an effective campaign is equally important. The campaign needs to immunize as many children as possible to stop the spread of the vaccine viruses.

WHO-vaccineThe Syrian cases are caused by vaccine-derived polioviruses — viruses from the oral polio vaccine used in some developing countries. The United States stopped using the oral vaccine in 2000.

Oral polio vaccine is made using live but weakened viruses; the original version contained components to protect against all three polioviruses, types 1 through 3. Type 2 polioviruses stopped circulating nearly 20 years ago and last year that component was removed from the oral vaccine.

While highly effective, the oral vaccine has some rare but serious side effects. The weakened viruses can spread from a vaccinated child to other children with whom he or she is in contact, also passively vaccinating them. But as the viruses spread from child to child they can mutate to become virulent again, regaining the power to cripple.

That’s what has happened in Syria. And there may be more cases, Zaffran acknowledged.

Genetic analysis shows the viruses from the three children are related and have been circulating for a period of about two years, Zaffran said. The fact that vaccine viruses have been circulating for that long suggests a lot of children in the region have not been successfully immunized against polio.

Zaffran said the new cases are a tragedy for the children affected and their families, but doesn’t change what health officials need to do operationally.

He said they learned a great deal in battling the earlier outbreak in Syria, “including how to work in these areas and which other partners are on the ground to help us implement.”

“To get our own staff into some of these areas will be very difficult if not impossible, so we will have to work through third parties,” he said.

Source: STAT News


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