Police official S.P. Rahim Shah told reporters that a bomb was planted near a vaccination post set up near a graveyard on Charsadda Road in Peshawar. Authorities put security in the district on a red alert following the incident.
The bombing marred the third round of a major polio vaccination campaign by the provincial government, which aims to inoculate 600,000 children against nine deadly diseases. Pakistan is one of only three countries in the world where polio remains endemic.
Islamist militants believe polio vaccine campaigns to be a cover for Western espionage and have frequently attacked health workers and their security teams. Local authorities have deployed 40,000 security forces for the third phase of the vaccination campaign in Peshawar.
Last month, six police officers providing security for a vaccination team were killed when a bomb struck their vehicle in Charsadda.
The U.N. World Health Organization recorded 91 new cases of polio in Pakistan last year, compared with 58 in 2012. Meanwhile, neighboring India last month was declared polio-free after no new cases were seen there in three years.
Ali is a special correspondent. Times staff writer Shashank Bengali contributed to this report from Mumbai, India.