KARACHI, Pakistan -- Usman, who limps on a leg bowed by the polio he caught as a child, made sure that his first three children were protected from the disease, but he turned away vaccinators when his youngest was born.
He was furious that the Central Intelligence Agency, in its hunt for Osama bin Laden, had staged a fake vaccination campaign, and infuriated by U.S. drone strikes, one of which, he said, had struck the son of a man he knew, blowing off his head. He had come to see the war on polio, the longest, most expensive disease eradication effort in history, as a Western plot.
In January, his 2-year-old son, Musharaf, became the first child worldwide to be crippled by polio this year.
"I know now I made a mistake," said Mr. Usman, 32, who, like many in his Pashtun tribe, uses only one name. "But you Americans have caused pain in my community. Americans pay for the polio campaign, and that's good. But you abused a humanitarian mission for a military purpose."
Anger like his over U.S. foreign policy has led to a disastrous setback for the global effort against polio. In December, nine vaccinators were shot dead in Pakistan, and two Taliban commanders banned vaccination in their areas, saying the vaccinations could resume only if drone strikes ended. In January, 10 vaccinators were killed in Nigeria's Muslim-dominated north.
Since then, there have been isolated killings -- of an activist, a police officer and vaccinators -- each of which has temporarily halted the campaign.
The war on polio, which costs $1 billion a year and is expected to take at least five more years, hangs in the balance. When it began 25 years ago, 350,000 people a year, mostly children, were paralyzed. Last year, fewer than 250 were, and only three countries -- Afghanistan, Nigeria and Pakistan -- have never halted its spread at any point.
While some experts fear the killings will devastate the effort here, Pakistan's government insists that they will not, and has taken steps to ensure that. Vaccinators' pay was raised to $5 a day in the most dangerous areas, police and army escorts were increased and control rooms were created to speed crisis responses.
But the real urgency to finish the job began earlier, for a very different reason. Two years ago, India, Pakistan's rival in everything from nuclear weapons to cricket, eliminated polio.
"Nothing wounded our pride as much as that," said Zulfiqar A. Bhutta, a vaccine expert at Aga Khan University's medical school.
Bill Gates, who is the campaign's largest private donor and calls beating the disease "the big thing I spend the majority of my time on," said Pakistan's desire to not be further humiliated "is our biggest asset."