The incident took place this morning when the team, guarded by policemen, were administrating polio vaccination drops to children at Shabqadar tehsil of Charsadda district.
Police said Sajid Khan, a team member, sustained a bullet shot and was rushed to a nearby hospital.
The armed assailants, meanwhile, managed to flee after the attack as police officials immediately cordoned off the area and launched a manhunt to nab them.
No one has taken responsibility for the attack but Pakistan faces massive resistance to its anti-polio efforts by the Taliban, which alleges that the vaccine is a conspiracy by the West to sterile Muslims.
Pakistan, Afghanistan and Nigeria are the three countries in the world where polio remains endemic.