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Vaccine-derived polio cases reported in Syria :

June 13, 2017

Syria is experiencing an outbreak of vaccine-related poliovirus, prompting a call for pediatricians to ensure travelers and refugees are properly vaccinated.

Strains of circulating vaccine-derived poliovirus type 2 (cVDPV2) were found in two people in Syria with acute flaccid paralysis and one healthy person, according to the Global Polio Eradication Initiative.

Wild poliovirus type 2 has been declared eradicated, however, when people receive live attenuated vaccines, the virus is shed in their stool. In areas with poor sanitation, it can spread.

“There are live vaccine viruses that continue to circulate in communities, and over time they can mutate and become infectious and cause paralysis,” said Yvonne A. Maldonado, M.D., FAAP, vice chair of the AAP Committee on Infectious Diseases.

The Academy and the Centers for Disease Control and Prevention’s (CDC’s) Advisory Committee on Immunization Practices recommend children in the U.S. receive four doses of inactivated polio vaccine (IPV), which protects against all three virus types.

The immunization schedule calls for doses to be given at ages 2 months, 4 months, 6 through 18 months, and 4 through 6 years and lays out additional guidance on timing and catch-up vaccination.

Dr. Maldonado said pediatricians should ask about patients’ travel plans, as some may need additional doses. CDC guidance on polio and travel is available at

“It’s apparent that immunity seems to wane over time so since we don’t really have polio in the Western Hemisphere we haven’t really had a problem, but if people go out of the country to areas where there may be polio, they need to get a dose of the killed vaccine,” Dr. Maldonado said.

Pediatricians also should ensure all children who recently entered the U.S. are vaccinated against all three types of poliovirus and will need to verify immunization status through documentation instead of antibody testing, according to CDC recommendations.

Syria is the second country with reported cases of cVDPV2 this year, along with the Democratic Republic of the Congo. Afghanistan and Pakistan have reported cases of wild poliovirus this year, according to the Global Polio Eradication Initiative.

Afghanistan, Nigeria and Pakistan had wild poliovirus cases last year and Laos, Nigeria and Pakistan reported cVDPV. Syria has not had a case of wild poliovirus type 1 since January 2014.

Last year, 155 countries switched from a live attenuated trivalent oral poliovirus vaccine to a bivalent vaccine that contains types 1 and 3. Vaccine campaigns using the bivalent vaccine were conducted in Syria in March and April this year, but their reach was limited due to the ongoing war in the region. Authorities say they are finalizing plans to respond to the new outbreak.

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