The United Nations suspended the work Wednesday after eight immunization workers will killed in three days. A ninth victim died Thursday after he was shot in the head.
Voice of America said most of the victims have been women.
No one has claimed responsibility for the attacks, but government officials in Peshawar said they believe a Taliban faction is responsible for at least some of them.
VOA said the Taliban have blocked similar programs in the past and have said polio vaccination efforts can act as a cover for spying.
The New York Times said Pakistan is one of three countries where the disease is still endemic.
Pakistan reported 198 new infections last year, the highest rate in the world.