A health worker administers polio vaccine to children during a three-day countrywide vaccination campaign in Peshawar, Pakistan, December 11, 2018. Pakistan is one of the last two countries, along with Afghanistan, where polio is still endemic. Though new polio cases dropped to a nine-year low worldwide in 2017, attacks by Islamist militants against health workers and the police guarding them has prevented a UN-funded vaccination campaign from being fully implemented.