The dead included six policemen and one child, Dawn.com reported.
A van was on its way to provide security to polio immunization workers in Khyber Pakhtunkhwa's Charsadda district at the time of the attack when a four- to five-kilogram device planted on a bicycle near the van was remotely detonated, the website said. The explosion destroyed the van.
The injured were taken to District Hospital Charsadda for treatment.
Meanwhile, in Punjab province's Bhakkar district, a polio vaccination team was attacked while traveling in a vehicle. The driver and one of the health workers were injured, Dawn.com reported.
On Tuesday, three health workers were killed in an attack on a polio vaccination team in Karachi. The provincial polio workers' association said it was halting operations in the Sindh province in response to the attacks.
Vaccination teams have become targets because the United States used one to help gather intelligence leading to the capture and killing of Osama bin Laden.