Experts warned that it is not yet time to let down guard on the swine flu pandemic.
The head of a panel advising the World Health Organisation on flu and pandemic alerts told an inquiry into the international response that the alert should not be wound down before an expected second wave in the southern hemisphere.
Australian disease expert John Mackenzie, chairman of the WHO's Emergency Committee, said he was waiting to see the progress of A(H1N1) influenza in the south's traditional autumn and winter flu seasons over the coming months.
"I don't think that we will terminate at any stage yet the public health emergency," Mackenzie said.
"Until we're certain, we can't lower our guard."
The Emergency Committee of scientists played a crucial role in recommending an international emergency over the new virus and different stages of alert, including the declaration of a pandemic.
It is due to meet again in the coming two or three weeks, Mackenzie revealed as he shed unprecedented light on decision-making in the highly confidential committee since April 24, 2009.
He told the inquiry that all recommendations to ramp up the alert level and maintain the pandemic status were made unanimously, often after "vigorous discussion" between the experts.
They were also followed nearly word-for-word by WHO Director General Margaret Chan, he added.
The inquiry set up by the UN health agency started this week to probe the global response to swine flu since it was uncovered in the United States and Mexico in April last year.
The review panel's questions were prompted by evidence that A(H1N1) flu has died down with the end of the flu season in the northern hemisphere, as well as doubts about its severity in terms of death and illness.
Mackenzie maintained that the virus was "certainly as severe" as those that sparked flu pandemics in 1957 and 1968, with the unusual characteristic of being more dangerous for young people and pregnant women rather than the elderly.
The external health experts also quizzed key actors in the WHO's decision-making about alleged influence from the pharmaceutical industry especially in the need for special mass vaccination.
The head of another scientific panel advising the agency on vaccines said "meticulous care" was taken to avoid conflicts of interest and to keep a distance from industry as far as possible.
David Salisbury, of the WHO's standing Strategic Advisory Group of Experts (SAGE) on immunisation, said members of the body were vetted.
"There has been no declaration of conflict from any SAGE member in our proceeding on A(H1N1) vaccine," added Salisbury, a senior British health official.
SAGE gave decisive technical advice to Chan last year on whether or not to produce a special vaccine for the A(H1N1) virus, the timing of production and vaccine needs.
Salisbury said pharmaceutical industry representatives were invited to take part in a consultation on vaccine production capacity and development.
"To my knowledge the industry has not done anything other than provide us with scientific information," he added.
"There was at no time any attempt to influence the advice we gave, either in the timing or the content of the advice we gave."
Mackenzie also defended his committee's safeguards.
The secrecy surrounding the identities of the other members of his panel and their work was precisely designed to protect them from commercial or state pressure, he insisted.
The 29 health experts on the inquiry -- who also include the Australian professor -- were wrapping up their first three day session on Wednesday.
More meetings are tentatively scheduled for the last weeks of June and September, with Internet correspondence in between.