When news broke last year that the CIA had run a fake vaccination program in Pakistan as part of the effort to track down Osama bin Laden, Wired's Maryn McKenna pointed out that the tactic

plays, so precisely that it might have been scripted, into the most paranoid conspiracy theories about vaccines: that they are pointless, poisonous, covert shields for nefarious government agendas meant to do children harm.

That is not speculation. The polio campaign has already seen this happen, based on just those kind of suspicions — not in a single poor slum in New Delhi, but across much of sub-Saharan Africa.

In the fall of 2003, a group of imams in the northern Nigerian state of Kano — the area that happened to have the highest rate of ongoing polio transmission — began preaching against polio vaccination, contending that what purported to be a protective act was actually a covert campaign by Western powers to sterilize and kill Muslim children. The president of Nigeria's Supreme Council for Sharia Law said to the BBC: "There were strong reasons to believe that the polio immunisation vaccine was contaminated with anti-fertility drugs, contaminated with certain virus that cause HIV/AIDS, contaminated with Simian virus that are likely to cause cancers."...Three majority Muslim states — Kano, Kaduna and Zamfara — suspended polio vaccination entirely....

The accusations that polio vaccination was a Potemkin cover for anti-Islamic activities almost ruined the international eradication of polio when they were false. Now, on the basis of the CIA's alleged appalling ruse in Pakistan, they may be made again. And they will be much more believable, because this time they might be be true.

Now jump to this month. The Guardian reports:

Two more workers in a polio eradication campaign have been shot dead in Pakistan in the latest in a series of attacks that have partially halted the UN-backed global health campaign to stamp out the disease. A third health worker was seriously wounded....

There were at least three separate attacks on Wednesday. In the north-western district of Charsadda, men on motorbikes shot dead a woman and her driver, police and health officials said.

Hours earlier, a male health worker was shot and badly wounded in the nearby provincial capital of Peshawar. He remains in a critical condition, said a doctor at Lady Reading hospital, where he is being treated.

Four other women health workers were shot at but not hit in nearby Nowshera, said Jan Baz Afridi, deputy head of the expanded programme on immunisation.

I'm not saying that there's a simple causal relationship between the intelligence-gathering scheme and the assassinations. The conspiracy theories did predate the revelation about the CIA. But as McKenna said, people are more likely to believe a theory when they've seen a substantial reason to suspect it's true.