1 of 5 View Caption

FILE- in this file photo dated Monday Nov. 25, 2013, a Pakistani child is vaccinated against polio by a health worker in Islamabad Pakistani girl Amina shows her thumb being marked after receiving polio vaccine in Lahore, Pakistan, Monday, May 5, 2014. For the FILE - In this file photo dated Tuesday Jan. 21, 2014, a Pakistani health worker gives a child a polio vaccine at the door way of FILE-- In this file photo dated Wednesday April 24, 2013, a Somali child receives a polio vaccine, at the Medina Maternal Child He A Pakistani health worker gives a child a polio vaccine in Lahore, Pakistan, Monday, May 5, 2014. For the first time, the World He