The explosion occurred in Ghalingan area of Safi tehsil area of Mohmand Agency when a polio vaccination team was passing through the area, official said.
The deceased were identified as Miskeen and Sahib Gul.
The injured were shifted to the nearby hospital.
Security forces have cordoned off the area and started search operation to nab the culprits.
Nobody claimed responsibility for the bombing.
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Pakistan is one of three countries where polio is still categorised as an endemic viral infection. The other two countries are Afghanistan and Nigeria.
Dozens of health workers and security personnel have died in attacks on polio vaccination teams in the northwest and the port city of Karachi.