Story highlights Official: Parents who sign affidavit vowing to vaccinate their children will be released

Pakistan has more new polio cases than any other country

Militants have targeted health workers administering vaccines for years

Islamabad, Pakistan (CNN) Police have arrested more than 500 parents in and around the northwestern Pakistani city of Peshawar for not allowing their children to get the polio vaccine, an official said Tuesday.

Peshawar Deputy Commissioner Riaz Khan Mehsud told CNN that the 513 arrests took place Monday and Tuesday as part of a government campaign to administer polio vaccines in parts of Pakistan's Khyber Pakhtunkhwa province.

Those arrested will be released on bail if they sign an affidavit stating that they will let their children get vaccinated, according to the deputy commissioner.

Pakistan's vaccination rate is inordinately low for a number of reasons, including attacks on medical workers, the displacement of people due to ongoing military operations and a lack of trust by some families.

Whatever the reason, the fact that a large number of children are not immunized is having an impact.

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