Senior World Health Organisation official Keiji Fukuda said this week that it was too early to declare the swine flu pandemic over, as it continues at "high levels" in parts of Europe and central .
Although the A(H1N1) flu virus is peaking and even declining in parts of the northern hemisphere, and is hardly present in the south, Mr Fukuda said there was an unproven possibility that there could be another wave later in the winter.
"It really probably remains too early to call the pandemic over," Mr Fukuda said in a weekly telephone news conference.
Mr Fukuda, Special Adviser to the WHO Director-General on Pandemic Influenza, said flu "activity continues at quite high levels in several different countries" notably the Czech Republic, France, Kazakhstan, Kyrgyzstan, Russia and Switzerland.
Mr Fukuda also noted that the signs of a peak and a decline in the caseload in parts of Europe had occurred "extraordinarily early for influenza," with several months of the winter left.
As a result, the WHO could not rule out the possibility of another wave in late winter or early spring.
"We simply are unable to answer this question right now. We continue to assess. Right now we cannot predict whether we will see another upsurge in activity in the earlier parts of 2010," Mr Fukuda said.
The WHO also pledged to continue support for the most vulnerable poorer countries by providing them with limited vaccine supplies even though the effort has been delayed.
So far, six vaccine makers and 12 countries had responded to a WHO appeal for help earlier this year with pledges of about 180 million doses of vaccine to be distributed to about 95 countries.
However, regulatory and safety checks and planning for distribution among health care workers and most vulnerable groups have proved more complicated than expected and the WHO hopes to start supplying needy countries soon.
"The first three countries that we are hoping to get vaccines out to are Azerbaijan, Afghanistan and Mongolia," said Mr Fukuda.
Mr Fukuda underlined that it was not too late for vaccine distribution.
"The pandemic virus is now a virus which has really spread around the world and it is quite likely that this is an infection that we will continue to see circulating for a number of years," he explained.
"It remains quite prudent to push ahead with the vaccination."
The global death toll since the swine flu pandemic first emerged in April is approaching the 10,000 mark, with at least 9,596 deaths recorded as of December 6, according to WHO data released last week.