The drive to rid the nation of Pakistan of polio has come to a virtual halt as World Health officials suspend the drive after a series of lethal shootings of polio workers.

The workers were directed to suspend operations today by the WHO and UNICEF after the latest shootings Wednesday where gunmen on motorcycles shot and killed a woman undertaking vaccination efforts and her driver. This brings the death toll of Polio workers to eight in the past 48 hours.

Prior to that fatal attack, a man working with the polio campaign was shot and severly wounded in the provincial capitol of Peshwar. Four other women were shot at but no injuries were sustained in that attack. Two other women were shot at in Charsadda, but no injuries were reported there either.

Although no one has taken responsibilty for the murders, suspicions fall on the Pakistani Taliban who have voiced their opposition to the polio campaign. They claim that the vaccinations are a sterilization program. Other Taliban say they will not let the vaccinations continue until drone attacks in their country come to a halt.

U.N. Secretary-General Ban Ki-moon is calling the murders of the workers “cruel, senseless and inexcusable.”

Thousands of workers were busy in the Asian country where polio is endemic. The Pakistan government says that some of the workers are continuing efforts to immunize, but many others refuse to go out. Protests over the shootings have taken place in Karachi and Islamabad.

The Pakistan government said that they did not expect attacks in areas far from areas held by the Taliban and say they were caught off guard and had to re-think their tactics for the campaign.

Global vaccination programs have eradicated polio in all but three countries in the world. Those countries are Nigeria, Afghanistan and Pakistan. Pakistan had 20,000 cases of the crippling disease in 1994, but through programs to vaccinate the public, that number dropped to less than 60 this year.