The CIA has ended the use of vaccine programmes in its spying operations amid concerns for the safety of health workers, the White House has said.
In a letter to US public health schools, a White House aide said the CIA stopped such practices in August. The CIA used a fake vaccine programme to try to find Osama Bin Laden before US special forces killed him in 2011.
The CIA's move comes after a wave of deadly attacks by militants on polio vaccination workers in Pakistan.
"By publicising this policy, our objective is to dispel one canard that militant groups have used as justification for cowardly attacks against vaccination providers," CIA spokesman Dean Boyd said in a statement to the BBC.