Health experts on Monday began a WHO probe into the controversial response to the first influenza pandemic of the 21st century, nearly a year after global alarm was raised over the new swine flu strain.
"We want to know what worked well. We want to know what went wrong and ideally why," World Health Organisation Director General Margaret Chan told the 29 health experts as they held their first meeting in Geneva.
"We want to know what can be done better and ideally how," she added.
The WHO formed the panel of experts following accusations that the agency-led international reaction to A(H1N1) influenza was overblown and may have been tainted by commercial interests.
The committee of experts from 28 countries will be chaired by Professor Harvey Fineberg, president of Washington's Institute of Medicine.
After the formative three-day meeting, the International Health Regulations review committee's work is expected to take about nine months, WHO spokesman Gregory Hartl said.
Chan promised an "independent credible and transparent" examination of the way the bolstered three-year-old International Health Regulations, which are designed to counter sudden threats from infectious diseases, had worked.
She said there would be no restrictions on its scope and emphasised that the WHO's management would come under scrutiny.
Specialists broadly defended the alarm over the discovery of A(H1N1) cases in Mexico and the United States in April 2009 as well as the WHO's declaration of a pandemic in June as the flu swiftly spread.
It has affected 213 countries and territories since then.
"I think they gave a terrific lead and were very authoritative. I think we have a lot to thank them for," John Oxford, a virologist and professor at Queen Mary's School of Medicine and Dentistry in Britain, told AFP.
"A lot of the criticism is political. I've not heard criticism from any virologist," he added, also highlighting the need to cater for impoverished countries with poor surveillance, care and health conditions.
Parliamentarians conducting a Council of Europe probe have criticised the transparency of decision-making and especially the potential influence of the pharmaceutical industry on a decision last year to press for vaccination.
That inquiry was set up after several governments sought to cancel mass orders of hundreds of millions of dollars worth of swiftly developed special pandemic vaccines after fears about the severity of swine flu died down.
Chan said the WHO had been "vigilant" in seeking out possible conflicts of interest among review committee members, who are mainly attached to national public health authorities in the WHO's 193 member states.
Although specialists also acknowledged flaws in the reponse, they insisted that vaccines were an essential weapon with the virus expected to surge again in forthcoming flu seasons.
"There's a tendency to have a post mortem at this stage but the patient is not dead," Oxford remarked.
David Heymann, a former head of infectious diseases at the WHO who left the agency in early 2009, insisted that public reticence towards vaccination in generally healthy Western populations had to be overcome.
The response to swine flu has been dogged by doubts since the early stages.
By the WHO's annual assembly in May 2009, several health ministers publicly urged Chan not to rush into declaring a pandemic, highlighting relatively mild symptoms and public doubts.
Heymann, chairman of Britain's Health Protection Agency, suggested that ways should be found to take into account severity of disease in pandemic alerts that primarily denote global geographic spread.
"The trouble is that early on, if you don't know the disease well, you have to take the most stringent measures," he cautioned.
Heymann and Oxford also emphasised that the effort was hampered by poor knowledge about the origins of A(H1N1) and its path from animals into humans, a general surveillance flaw that Chan also acknowledged last week.