The CIA recently admitted to aPhoto:  New York Times fake vaccination plan that gathered DNA samples from villagers while the CIA tried to track down Osama Bin Laden in Pakistan.  Since then, Pakistani tribal leaders and the Taliban in Pakistan, where polio still had a foothold, have convinced locals to shun the legitmate vaccine programs now trying to innoculate against polio.  The rise in polio cases in Pakistan has skyrocketed since then. 

The New York Times recently published an article about this.  You can read about this in more detail here:  http://www.nytimes.com/2012/07/10/health/cia-vaccine-ruse-in-pakistan-may-have-harmed-polio-fight.html?pagewanted=all&_r=0