The bomb reportedly hit a police van accompanying health workers participating in a drive aimed at immunizing young children.
"The police team had arrived to escort teams for the polio campaign," Ahsan Mehboob, the provincial police chief, told Reuters. He added, "It was a suicide blast, we have gathered evidence from the scene."
According to Reuters, two groups claimed responsibility: the Pakistani Taliban and Jundullah, which has ties to the Taliban.
In 2011, the CIA orchestrated a fake vaccination drive at a polio facility in Abbottabad as part of the hunt for Osama Bin Ladin. Since then, facilities in the region and their workers have fallen under distrust.
A spokesperson for Pakistan's Ministry of Foreign affairs last year criticized the CIA for undermining world health efforts to eradicate polio, pointing out that it "further reinforced the negative perception about the agenda behind the polio eradication campaign."
Pakistan and Afghanistan are the only two remaining countries in the world where polio continues to be transmitted.
