The pharmaceutical giant GlaxoSmithKline claims to have created the most effective vaccine so far against the deadly H5N1 strain of bird flu.
GlaxoSmithKline (GSK) says its vaccine produces the highest reported immune response at a low dosage because of a special "adjuvant" - an ingredient which stimulates the immune system and boosts the body's response to the vaccine.
The vaccine - which has not yet been peer-reviewed - could be used in lower doses, making it cheaper to produce, BBC Radio 4's Today programme reported.
GSK chief executive JP Garnier hailed it as "a big breakthrough" and said the company could produce hundreds of millions of doses by Christmas.
No final decisions have been made about cost, but it could as little as £4 a dose.
Earlier this month Spain reported the discovery of its first case of H5N1 in a wild bird.
Mr Garnier told Today: "We have used this special adjuvant and now we are able to demonstrate very significant and totally satisfactory efficacy and safety with a dose that is only 3.8 microgrammes.
"The meaning of this is that we are going to be in a position, starting later this year, to produce hundreds of millions of doses of an effective pandemic vaccine, so this is a big breakthrough."
He added: "We do not know what it would cost because we still have one unknown, which is we have to industrialise the process to make the vaccines.
"But I would say if you were a betting man, you would say probably it's going to be equivalent to a flu vaccine in terms of cost - maybe £4 a dose or so.
"We need a little more time to answer those questions but by Christmas we will be able to do so."
Mr Garnier continued: "If we had a pandemic threat - an immediate threat - and we needed to switch from flu to pandemic, then we would make significant quantities very quickly."
Asked if the vaccine could deal with a possible mutation in the virus that meant it passed from human to human, Mr Garnier replied: "If you had a mutation that is closely connected to the H5N1 virus, the answer is probably yes.
"If the virus jumps away from H5N1 to a completely different kind of virus, then the answer is our vaccine would probably not be effective but the work that we have done would be very helpful because we would be in a position now to immediately produce the new vaccine as soon as we have identified the new virus."
Mr Garnier said GSK was concerned about the potential cost of the vaccine for less developed countries, which have so far been hardest hit by H5N1.
He added: "We need to find a source of funding and the Global Fund and the Gates Foundation are just two examples of organisations with significant money that have in the past committed to vaccination campaigns and we are in discussion with some of those organisations."
Tests in Belgium found that doses of just 3.8 micrograms produced an immune response in more than 80% of people.
GlaxoSmithKline said 400 adults had been given two vaccinations during the course of the trial at various dosages - 3.8 micrograms being the lowest.
The trial found that four-fifths of those given that dosage showed evidence of producing antibodies, something which was detected by measuring whether red blood cells clump together.
Antibodies prevent the cells from grouping together.Reuse content