Senior police official Sadiq Baluch said the attack took place in the village of Gandi Umar Khan, about 20 kilometers (12 miles) West of the nearest city of Dera Ismail Khan, on Tuesday, press tv reported.
There was no immediate claim of responsibility, but suspicion quickly fell on the Taliban as they oppose the polio vaccination campaign and have been accountable for similar militant attacks in the past.
The Taliban accuse health workers of acting as spies for the United States, claiming the polio program is part of a Western plot to sterilize Muslim children.
Earlier this month, a bomb attack on a polio vaccination team killed at least 11 people in Northwest Pakistan.
The World Health Organization (WHO) says Pakistan, alongside Afghanistan and Nigeria, is a country where polio remains endemic. The UN agency has warned that the city of Peshawar in Northwest Pakistan is the world’s “largest reservoir” of polio.
According to the WHO, Pakistan recorded 72 cases of polio in 2013. The figure marks an increase of 14 cases from the number registered in the South Asian country in the preceding year.