Barack Obama's top anti-terror adviser has pledged that the CIA will no longer use vaccination programmes - the ruse used to target Osama bin Laden before the US raid that killed him in 2011 - as cover for spying operations.

Lisa Monaco wrote to the deans of 13 prominent public health schools last week, saying the CIA agreed it would no longer use vaccination programmes or workers for intelligence purposes.

The agency also agreed to not use genetic materials obtained through such programmes.

Pakistani doctor Shakil Afridi provided hepatitis vaccinations in the city of Abbottabad as cover for his CIA-backed effort to obtain DNA samples from children at a compound where al Qaida mastermind bin Laden was later killed during the raid by US Navy SEALs.

Dr Afridi was convicted and sentenced by a Pakistani court to 33 years in prison for treason, but the sentence was later overturned and he now faces a retrial.

The health school deans were among a group of medical authorities who publicly criticised the CIA's use of the vaccination programme after it was disclosed by media accounts and Pakistan's arrest of Dr Afridi as a CIA operative.

In her May 16 letter to the health school deans, Ms Monaco said the US "strongly supports the Global Polio Eradication Initiative and efforts to end the spread of the polio virus forever".

She added that CIA director John Brennan promised last August that the agency would "make no operational use of vaccination programmes, which includes vaccination workers".

Also saying no DNA or genetic material would be used from such programmes, Ms Monaco said the CIA policy "applied worldwide and to US and non-US persons alike".

CIA spokesman Dean Boyd said Mr Brennan "took seriously the concerns raised by the public health community, examined them closely and took decisive action".

Ms Monaco's letter and the CIA statement did not acknowledge any error in the decision to use the Pakistan vaccine program as a spying cover. The letter was first disclosed in a report by Yahoo News.

The White House statement came three days after Pakistan acted to quell a growing polio crisis within its borders. The public health deans had warned last year that the CIA's use of a vaccination programme had played a role in the shootings of several health workers in Pakistan and could hamper anti-polio efforts.

"Public health programmes should not be used as cover for covert operations," they said.

Last week, Pakistan's Health Ministry announced that it would require that all travellers leaving the country first receive a polio vaccination. That move followed the World Health Organisation's declaration earlier this month that polio's spread was an international public health emergency.

The WHO identified Pakistan, Syria and Cameroon as nations that had allowed polio to spread beyond their borders.

Pakistan was the only country with reported endemic polio that saw a rise in new cases in 2012, the health organisation said. Pakistan accounted for more than a fifth of all polio cases identified across the world in 2013.

The CIA's use of a polio vaccine program to spy on bin Laden's compound undercut President Obama's own high-profile speech to the Muslim world in 2009, in which he touted US efforts to slash the growth of polio in Pakistan, Afghanistan and Nigeria.

With Obama administration assurances, Muslim scholars in two international groups issued religious decrees urging parents to vaccinate their children.