Two children in the Deir-Ez-Zor governorate in eastern Syria have been paralyzed by the vaccine viruses. The virus has been recovered from a third child who was not paralyzed. All signs point to vaccine viruses that are circulating in the area.

Detailed planning is already underway for emergency vaccination programs to reach about 200,000 children in the region, Michel Zaffran, head of the WHO’s polio program, told STAT. The government of Syria has made a formal request for the emergency vaccination effort, he said.

Given the six-year-old civil war in that country, the endeavor will be logistically challenging. But Syria experienced a polio outbreak in 2013 and 2014, and it was extinguished.