Islamabad , Pakistan ( CNN ) -- Health workers administering polio vaccinations to children came under attack in northern Pakistan on Tuesday , killing their police escort , authorities said . Two women administering the shots entered a house on the outskirts of Mardan when two assailants on a motorbike opened fire of them , according to Danishwar Khan , a local police official . The women were not injured . Attacks like these have become a frequent occurrence in some parts of Pakistan and have left 10 workers dead . Pakistan is one of three countries in the world where polio has yet to be eradicated . Read more : At the U.N. , a vow to eradicate polio by 2015 . Pakistanis have viewed polio vaccination campaigns with suspicion after the CIA 's use of a fake vaccination program in 2011 to collect DNA samples from residents of Osama bin Laden 's compound to verify the al Qaeda leader 's presence there . Bin Laden was killed by U.S. forces in May 2011 . In June , a Taliban commander in northwest Pakistan announced a ban on polio vaccines for children in the region as long as the United States continues its campaign of drone strikes in the region , the Taliban said . It was n't immediately clear if the Taliban played a role in Tuesday 's attacks . Polio , a highly infectious viral disease that can cause permanent paralysis in a matter of hours , has been eradicated around the world except for three countries where it is endemic : Pakistan , Nigeria and Afghanistan . After the number of cases spiked sharply last year , Pakistan stepped up its eradication efforts . The numbers fell from 173 in 2011 to 58 in 2012 , according to the Global Polio Eradication Initiative .
NEW : Pakistan is one of three countries in the world where polio has yet to be eradicated . NEW : The Taliban announced a ban on polio vaccinations in June . 10 workers have been killed in recent months . Pakistanis have viewed polio vaccination campaigns with suspicion .