The smaller the dose, the more number of shots that can be delivered per quantity of vaccine and the firm hailed the achievement as a "significant breakthrough."
GSK said it has developed the vaccine using a proprietary new adjuvant that does not use aluminum salt (alum), the conventional adjuvant that has been widely used since the 1940s, designed to enhance the body's immune response to the antigen contained within the treatment.
With the global vaccine market booming, GSK is currently engaged in an arms race with other big vaccine manufacturers such as Chiron and Sanofi Pasteur to develop new vaccine formulations that do not use alum, as although it is regarded as generally safe and cheap, it only prevents degradation or discharge of the antigen and does not have any immunostimulatory properties in its own right, something expected from a modern adjuvant today.
In a yet-to-be published study in 400 patients in Belgium, GSK said its new bird vaccine enabled over 80 per cent of subjects who received 3.8µg of antigen to demonstrate a strong seroprotective immune response.
"This is the first time such a low dose of H5N1 antigen has been able to stimulate this level of strong immune response," said the company in a statement.
"Efficacy results at these levels of antigen dosage have also not been reported for any other H5N1 vaccine in development to date, including those using other adjuvants such as alum."
The company announced it plans to make regulatory filings for the vaccine in the coming months and said hundreds of millions of doses could be produced by early 2007, after which time governments could order the vaccine for delivery and stockpiling.
However, the new vaccine still uses the traditional method of vaccine production, requiring the it to be grown in chicken eggs, a process that is cumbersome and takes several months, limiting the amount of vaccine that can be manufactured quickly on a mass scale.
Still, as pressure mounts on global vaccine makers to develop enough quantities of an effective vaccine to protect the world's population in the event of a bird flu pandemic, GSK's revelation brings hope of relieving some of this pressure.