Gunmen fatally shot a police officer assigned to protect polio workers in Pakistan’s northwest, an official said Monday. At least 11 police have died this year while on security duty for vaccination campaigns in Khyber Pakhtunkhwa province. The gunmen fired at a team working in the Wargari area of Lakki Marwat district, said police official Sajid Khan. One of the attackers also died, while the remaining assailants fled. No one immediately claimed responsibility for the assault. Anti-polio campaigns in Pakistan are regularly marred by violence. Militants target vaccination teams and police assigned to protect them, falsely claiming that the campaigns are a Western conspiracy to sterilize children. 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. The potentially fatal, paralyzing disease mostly strikes children under age 5 and typically spreads through contaminated water.