Almost one million Pakistani children were left out of a polio vaccination drive which ended Wednesday, officials said, as unrest and flooding limited access and some parents viewed the campaign as a Western "conspiracy".
Data obtained by AFP showed that some 998,569 children of the 32 million targeted during the three-day nationwide drive, backed by the government and World Health Organization, were left unvaccinated against the crippling disease.
Earlier this year, a Pakistani doctor was jailed for helping the CIA track down Al-Qaeda chief Osama bin Laden in 2011 using a fake hepatitis vaccination programme, leading the Taliban to ban immunisation in some areas.
WHO Senior Coordinator for Polio Vaccination Dr. Elias Durry said the huge number of missed children was a "cause of concern".
"While we can celebrate the achievement of vaccinating millions of children during every polio campaign, finding and vaccinating the repeatedly missed children should be the top priority of all the polio teams across the country."
Government health officials said that most of the one million children remained unvaccinated because of access issues, unrest in southwestern Baluchistan province and flooding in many parts of southern Sindh province.
They added many parents in militancy-hit northwestern Khyber Pakhtunkhwa still view immunisation as a "conspiracy."
In less turbulent areas, health workers failed to carry-out follow up visits or make enough effort to visit houses "far away".
Unknown gunmen on Tuesday killed a polio vaccinator in the Killi Jeo area of Baluchistan's capital Quetta, a day after the campaign kicked off, senior government official Tariq Mengal told AFP.
Pakistan is one of only three countries where the highly infectious crippling disease remains endemic, along with Afghanistan and Nigeria.
There have been 30 confirmed cases of polio in Pakistan this year according to the government, 22 of them in the tribal areas bordering Afghanistan.