The police said that the cop, identified as Shahnawaz, was killed in the Suleman Khel area of Peshawar as he was going to perform his duty. No one immediately claimed responsibility for the assault.
A search is underway to arrest the culprits, police said.
At least 12 police have died this year while on security duty for vaccination campaigns in Khyber Pakhtunkhwa province.
Anti-polio campaigns in Pakistan are regularly marred by violence. Militants target vaccination teams and police assigned to protect them.
A five-day anti-polio campaign started Monday in nine high-risk districts of Khyber Pakhtunkhwa. Health workers are tasked with administering vaccines to some 3.28 million children under age 5. More than 26,000 police are protecting the teams.
Pakistan and neighboring Afghanistan are the only countries where the spread of polio has never been stopped.
Pakistan on Saturday reported the fourth poliovirus case of the current year, sources within the Ministry of National Health said.
A 2-year-old boy from Bharkan union council in Sindh’s Shikarpur district became the latest victim.