China appears to have beaten the world to a bird flu vaccine

Scientists in China have developed a potential vaccine against the deadly H5N1 bird flu virus currently sweeping across Asia.

The vaccine has raised hopes for the rapid protection of millions of people should the virus mutate into a pandemic form.

The vaccine is made up of an inactivated sample of the existing H5N1 avian flu virus with the addition of an adjuvant that enhances the immune response.

In trials of the vaccine on 120 volunteers it produced a good immune response and possibly has the potential to be mass produced in an emergency to provide protection for 675 million people.

The volunteers aged between 18 and 60 were given either a dummy formula or the vaccine at doses of 1.25, 2.5, 5 and 10 micrograms with aluminium hydroxide as the adjuvant.

Within 56 days, the researchers say all of the vaccine doses produced antibodies against the virus, with the best response in the 10-microgram group which stimulated 78 per cent protective antibodies.

This level of protection exceeds the European Union minimum requirement of 70 per cent.

The vaccine was well tolerated with very few side-effects.

Sinovac Biotech, a Beijing-based pharmaceutical company, jointly developed the vaccine along with the Chinese Science and Technology Ministry and the country's Centre for Disease Control and Prevention.

Dr. Iain Stephenson of Leicester Royal Infirmary, U.K., an infectious disease specialist says the advantage of the Chinese design was the successful use of a whole virus, rather than parts of it, to stimulate an immune response.

Whole-virus vaccines are evidently known to trigger a bigger immune response, although they often cause more side-effects.

Experts say because the dosage is lower than in previous vaccines, more could be produced in the crucial first six months after the start of a pandemic.

They say it will be easier to modify an existing vaccine for the pandemic strain if the safety of the vaccine design has already been shown and a dose-sparing approach could be crucial for a global supply of pandemic vaccine.

At present, should a pandemic occur, the demand for influenza vaccines will far outstrip the manufacturing capacity of such vaccines, says study author Weidong Yin, CEO of Sinovac Biotech.