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LONDON, England (Reuters) -- A bird flu vaccine for humans that uses only a very low dose of active ingredient has proved effective in clinical tests and could be available in 2007, its maker GlaxoSmithKline Plc has said.
The promising result means Europe's biggest pharmaceuticals group is on track to start making the vaccine in commercial quantities by the end of the year.
Glaxo believes its H5N1 vaccine will work more efficiently than rival ones in development because of the proprietary adjuvant used in its manufacture. Adjuvants are additives put into vaccines that boost the immune system and make it respond more efficiently.
A key challenge in the race to produce a vaccine for millions of people around the world -- which governments are keen to stockpile -- is how to make the maximum number of shots from the minimum amount of antigen, or active ingredient.
Glaxo's vaccine contains just 3.8 micrograms of antigen, yet more than 80 percent of healthy adult volunteers who received two doses had a strong immune response.
That level of protection meets or exceeds requirements set by regulatory agencies for approving new flu vaccines, and is twice as good at half the dose as results with an experimental vaccine produced by Sanofi-Aventis.
Breakthrough
Glaxo Chief Executive Jean-Pierre Garnier said it was a "significant breakthrough."
"All being well, we expect to make regulatory filings for the vaccine in the coming months," he said.
Sanofi in May reported good responses with a vaccine using a conventional adjuvant given at two doses of 30 micrograms. But when the dose was reduced to 7.5 micrograms, only 40 percent of people were protected.
While Glaxo's vaccine offers protection against the deadly H5N1 avian flu virus now circulating, its impact on any mutated strain of virus is not certain.
However, experts say it could "prime" a person's immune system so they will get stronger effects from a later, better-matched vaccine.
Glaxo said it would now also study the ability of its vaccine to offer cross-protection to variants of the H5N1 virus.
The H5N1 strain of avian influenza has spread rapidly out of Asia and has killed more than 130 people who have come into close contact with infected birds.
Experts fear it could trigger a global epidemic of flu that could kill millions, if it acquires the ability to pass easily from human to human.
Companies are racing to develop pandemic H5N1 vaccines that could save lives and buy time to develop a vaccine against a pandemic strain. It could take from four to six months from the start of a pandemic before a specific vaccine will be ready.
Other firms working on a bird flu vaccine include Novartis AG and Baxter International Inc