Arifullah Khan had just administered another polio vaccine when the gunfire blasted from the nearby hills. "It happened so suddenly.There was so much gunfire it felt like an explosion," he said, recalling details of the attack five years ago in Pakistan’s Bajaur tribal region near the Afghan border.
A bullet shattered his thigh and he fell to the ground. His childhood friend and partner in the vaccination campaign, Ruhollah, lay bleeding on the ground in front of him.