UK drugs firm GlaxoSmithKline believes it has developed a vaccine for the H5N1 deadly strain of bird flu that may be capable of being mass produced by 2007.
The threat of a bird flu pandemic has companies racing for a cure
The vaccine has proved effective at two doses of 3.8 micrograms during clinical trials in Belgium, BBC business editor Robert Peston has learned.
It is the size of the dose that is highly significant, Glaxo explained.
Firms want the smallest effective dose so that they can get the maximum number of shots out of a quantity of vaccine.
"It is good news that this vaccine can produce a significant response from a relatively small dose," said Dr Donald Cutler, principal lecturer in infectious diseases at University of East London.
Glaxo has yet to publish the results of its tests.
The news of the work on a potential vaccine came as Glaxo reported its profits had risen 14% in the three months to June to £1.32bn (US$2.4bn).
Glaxo said that governments could order the vaccine for delivery and stockpiling in early 2007.
One of Glaxo's main rivals, the French drug company Sanofi Aventis, has also been working on a vaccine.
Drug companies are looking to develop treatments because of concerns that the H5N1 virus will combine with a human flu virus and mutate into a form which can spread between humans.
Bird flu has been spreading outwards from Asia
But a number of firms, including Glaxo, are seeking to develop vaccines based on the existing H5N1 strains to give humans some form of protection.
Its vaccine is on a fast track for approval with the relevant licensing authorities - the US Food and Drug Administration (FDA) and the European Medicines Evaluation Agency (EMEA).
"All being well, we expect to make regulatory filings for the vaccine in the coming months," said Glaxo chief executive Jean-Pierre Garnier.
The UK and US have both indicated a desire to "prime" their respective populations with an initial inoculation.
Glaxo's Garnier has spoken to US President Bush about the vaccine
Mr Garnier said he recently met US President George W Bush to discuss the vaccination programme.
Following that meeting, Glaxo received $272m (£148m) of funding, earmarked in part to develop new technologies to produce vaccines.
If there was a pandemic outbreak in the early autumn, mass manufacture of Glaxo's vaccine could probably be started quickly by collaborating with rival pharmaceutical companies.
Glaxo said it was also talking to the Gates Foundation about how to provide the vaccine to poorer, developing countries.
Despite the company's optimism, a number of unanswered questions remain.
Firstly, there is uncertainty over how many doses can be manufactured quickly, and how easy it would be to switch from laboratory testing to mass production.
And secondly, it is not clear how effective the vaccination would be if H5N1 were to mutate significantly.
Chicken flu and other viruses often go through a process of mutation
Glaxo says its vaccine is more akin to shotgun treatment than a "precision-rifle cure", which means that it appears to be effective against small mutations in the virus strain.
Glaxo said the cost of the vaccine is likely to be a little more than for conventional flu vaccines, which retail for about £4 per shot.
"The vaccine is an affordable option ahead of a pandemic emerging," said Ian Jones Virology professor at Reading University.
According to Glaxo, the side effects to its bird flu vaccine have been limited to a fever in a number of patients.