In some areas, hundreds of thousands of children have gone without a polio vaccination
A prominent religious seminary in Pakistan has backed polio vaccinations, saying they are not un-Islamic.
The decree was issued by the school's head, Maulana Sami ul-Haq, who urged parents to immunise their children.
The fatwa comes amid a decade-long campaign of violence by Islamist groups against health workers who they accuse of being spies or part of a Western plot to sterilise Muslims.