In the course of trying to prove that it was actually Osama Bin Laden living in that compound outside Abbottabad, the CIA apparently set up a fake Hepatitis B vaccination campaign, which was actually aimed at collecting DNA samples from Bin Laden's children. Working with a Pakistani doctor, they started giving out the first dose of the three-dose vaccine in poor neighborhoods, as a cover, and then, instead of going back to administer the necessary follow-up doses (without which, children are still susceptible to the disease) they moved on to the area where Bin Laden lived and tried to get the doctor inside his compound.
This is bad. Very bad, from a public health perspective. The New York Times story linked above doesn't really get into the implications the CIA's (failed) venture will have for real vaccination campaigns, but Maryn McKenna does a great job of explaining the issues at her Wired blog:
It 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."
The rumors caught like wildfire, and they were spread further by political operatives who saw an opportunity to disrupt a recent post-election power-sharing agreement between the Muslim north and the Christian south. Three majority Muslim states — Kano, Kaduna and Zamfara — suspended polio vaccination entirely. Vaccination acceptance in the rest of the country fell off so sharply that the national government was forced to act. It ordered tests of the vaccine by Nigeria's health ministry and empaneled a special commission to visit the Indonesian labs where the vaccine administered in Nigeria was made. The WHO convened emergency meetings.
And polio began to spread. At the end of 2003, when the boycott began, there had been only 784 known polio cases in the entire world. By the end of 2004, there had been 793 new cases just in Nigeria. Polio leaking across Nigeria's borders reinfected Benin, Botswana, Burkina Faso, Cameroon, Chad, the Central African Republic, Cote d'Ivoire, Ethiopia, Ghana, Guinea, Mali, Sudan and Togo. Nigerian strains appeared in Yemen, site of the largest port on the Red Sea, and in Saudi Arabia, imperiling the millions of pilgrims coming to the country on hajj.