Polio workers and their security guards are under constant threat in Pakistan.
A total of 76 workers have been murdered in the last two years.
Islamists believe the vaccine is a Western plot to sterilize the population.
A Pakistani police officer, left, stands guard while health worker Shahida Akram, 41, prepares polio vaccines to be given for children in a neighborhood in Islamabad, Pakistan, Wednesday, Jan. 30, 2013. Some Islamic militants oppose the vaccination campaign, accuse health workers of acting as spies for the U.S. and claim the polio vaccine is intended to make Muslim children sterile. Pakistan is one of the few remaining places where polio is still rampant. (AP /Muhammed Muheisen)
Two more female polio workers were gunned down this week in Mansehra, Pakistan.
Islamists have murdered 76 polio workers total since December 2912.
Gunmen on Tuesday killed two women who were members of a polio vaccination team and a police guard in Mansehra, the latest in a spate of deadly attacks on the teams.
Police said unknown gunmen fired at workers Kaneez Nargis and Farah Gul as they gave polio drops to children in Mansehra’s area of Dana. Police constable Ishfaq was also killed in the attack.
Senior local police official, Akhtar Hayat, confirmed the incident and casualties.
Pakistan is one of only three countries where polio remains endemic.
Attempts to eradicate it have been badly hit by militant attacks on immunisation teams that have claimed 76 lives since December 2012.