The CIA gained some intel that Bin Laden was residing in Pakistan, and in the precise vicinity, but they wanted to be certain. They way they did this was by recruiting a local doctor [1] and splashing around a ton of money to start a fake vaccine campaign. It's unclear if they bothered using real vaccines or not, but the entire point of the program was a CIA DNA collection program. The CIA was bulk harvesting Pakistani DNA and cross referencing it against DNA from Bin Laden's sister
Once it was confirmed that Bin Laden had children in the area, the program was scrapped, we invaded, he was killed, and everybody was left out to to dry. The doctor was imprisoned, charged with treason, and has since been in solitary with claims of torture for going on a decade now [2]. Local aid workers (who had no idea what they were involved in) were hunted down and killed, some districts banned vaccination drives, and Pakistanis have been extremely critical of any sort of vaccination effort since.
[1] - https://en.wikipedia.org/wiki/Shakil_Afridi
[2] - https://nationalinterest.org/blog/buzz/ten-years-what-became...