In Pakistan, attempts to eradicate polio stalled when the vaccination programme became tangled in international politics, religious decrees and social media scare stories. Vaccination workers have been attacked and even killed. BBC Urdu’s Shumaila Jaffery met vaccination workers, parents, and clerics for a BBC World Service series, "Vaccines: A Crisis of Trust".

(Image: Doctor vaccinates child against polio. Credit: BBC)