The doctor, Constant Dedo of Ghana, was shot in the abdomen, while the driver suffered a grazing wound to his neck. They are out of danger, Yunus said, adding that the motive for the attack was under investigation.

One of only three countries where polio is endemic – Nigeria and Afghanistan are the others – Pakistan is aiming to immunize 34 million children under age 5 in a campaign that runs through Wednesday. So far this year, new cases of polio are down from last year’s record of nearly 200 cases. The tribal zone, known formally as the Federally Administered Tribal Areas, or FATA, is the most difficult region for the polio work.

Ali, the prime minister’s adviser, said a government public relations campaign has reduced opposition to vaccinations.

“We’re telling them that this (Shakil Afridi story) is a complete misconception. Don’t deprive your child of a safe and healthy life because of what Shakil Afridi did,” Ali said.

Last month, two senior Pakistani Taliban commanders who control large parts of South Waziristan and North Waziristan in the tribal area issued bans on polio vaccinations in their areas. Polio work has also been stopped in districts of Khyber agency, another part of the tribal area, on the orders of another Islamist warlord, putting tens of thousands more children at risk.

Pakistani officials are in negotiations with the militants over the ban, but they weren’t able to convince them to overturn it ahead of the immunization drive, so the campaign was postponed there on Monday. The ban in North and South Waziristan means that about 280,000 children there cannot be reached for the polio drops, Ali said.

In a leaflet last month, Maulvi Nazir, who holds sway over the upper half of South Waziristan, accused health workers who administer anti-polio drops of being U.S. spies, and he also said that the ban on the immunizations wouldn’t be lifted until missile strikes by U.S. drone aircraft ended in the tribal areas.

“In the garb of these vaccination campaigns, the U.S. and its allies are running their spying networks in FATA which has brought death and destruction on them in the form of drone strikes,” the leaflet said.