Washington - The White House has promised the US will not use vaccination programmes as cover for spy operations - after the move was attempted during the hunt for Osama bin Laden in Pakistan.
As Pakistan suffers a resurgence of polio, a top White House official pledged in a letter dated 16 May that intelligence agencies would forswear the tactic, which is partly blamed for the spread of the crippling disease.
Islamic militant leaders are reluctant to embrace vaccination programmes after Pakistani doctor Shakil Afridi attempted to help the CIA track down the al-Qaeda terror chief through a fake vaccine project.
President Barack Obama's top White House anti-terrorism advisor Lisa Monaco told deans of 13 US schools of public health that CIA chief John Brennan had directed last year that agents would "make no operational use of vaccination programmes".
"Similarly, the agency will not seek to obtain or exploit DNA or other genetic material acquired through such programmes."
"This CIA policy applies worldwide and to US and non US persons alike."
'Cover for foreign spying'
The letter by Monaco was first reported by Council on Foreign Relations fellow Laurie Garrett on Twitter and by Yahoo News.
Pakistan last week announced that residents of its restive tribal belt would not be able to travel to other parts of the country without getting vaccinated against polio.
The order came days after Pakistan said it would set up mandatory immunisation points at airports to help stop its polio outbreak spreading abroad, in response to new guidelines by the World Health Organization (WHO).
The WHO warned that polio has re-emerged as a public health emergency - with the virus affecting 10 countries worldwide and becoming endemic in three, including Pakistan - and urged infected nations to implement vaccine requirements for all international travel.
The Taliban and other militants violently oppose polio vaccination campaigns, seeing them as a cover for foreign spying and regularly attack immunisation teams. Some 56 people have been killed in such incidents since December 2012.
The CIA reportedly engaged Afridi to stage a fake vaccination campaign in the city of Abbottabad, Pakistan where the al-Qaeda leader was eventually killed in a daring US special forces raid in 2011.
The idea had apparently been for the doctor to secure DNA material after vaccinating bin Laden's children, as a way of positively identifying the al-Qaeda leader.