From 2012-15 half a million children in the tribal areas in northwestern Pakistan were inaccessible to vaccinators. The mountainous region was controlled by militant groups that prohibited polio vaccinations. After a military offensive more than 1 million civilians fled to refugee camps. The refugee crisis created an opportunity for vaccinators to reach hundreds of thousands children, says Dr Malek Sbih of the WHO. “The military operation provoked an enormous exodus of people from the region. It’s unfortunate. But fortunately for us, it gave us the opportunity to reach 265,000 kids.”

Photograph: Waseem Niaz/Unicef