"With influenza vaccine production capacity on the rise, we are beginning to be in a much better position vis-a-vis the threat of an influenza pandemic," said Marie-Paule Kieny, director of the WHO's Initiative for Vaccine Research.
Pharmaceutical manufacturers including global giants Novartis, GlaxoSmithKline and Sanofi-Pasteur have been able to boost production of trivalent seasonal flu vaccines to around 565 million doses from 350 million in 2006, Kieny told journalists.
The International Federation of Pharmaceutical Manufacturers and Associations expects to be able to ramp up capacity to one billion doses in 2010 providing demand exists, she added.
This could result in around 4.5 billion doses of pandemic vaccine, which uses eight times less antigen -- the substance that stimulates an immune response -- than a seasonal dose, the WHO said.
However, Kieny stressed this was still short of the WHO's target of being able to provide a vaccine to all of the world's 6.7 billion people within six months of a pandemic being declared.
The WHO has set up a special advisory group to report to the organisation's director general, Margaret Chan, on the issue.
The group met behind closed doors last week and agreed to promote seasonal flu vaccine programmes (thus stimulating demand), then encouraging the pharmaceutical industry to maintain production capacity beyond seasonal demand.
The WHO warned earlier this month that European plans to cope with any possible flu pandemic have major weaknesses which might lead to chaos.
It warned that many European governments risked "chaotic service responses and public anxiety" by leaving it up to regional or local authorities to organise drug delivery during a pandemic and giving them little guidance.
Scientists fear that the H5N1 strain of bird flu, which emerged in humans in Asia in the 1990s, could mutate into a more virulent form that could easily be passed between humans, triggering a global flu pandemic with the potential to kill millions.
Some 329 people have contracted H5N1 bird flu since 2003, of whom 201 have died, according to the WHO. Most of the human cases have been in Asia but it has also spread to the Middle East and Nigeria.