Bird flu vaccine - experts say let's try harder

Mar 6 2007

Experts on viruses are calling for a bigger effort to be made in developing vaccines to tackle pandemics.

They are also warning that although it is widely considered that the H5N1 bird flu virus currently circulating is the most likely candidate, the world could be losing sight of the big picture and other potential virus strains could also prompt a pandemic.

The virologists say flu vaccines should be "broad-based" and protect against as many virus strains as possible, otherwise all contingency plans will be in vain.

At a medical conference in Hong Kong one expert, Albert Osterhaus, virology professor at the Erasmus Medical Centre in Rotterdam, has reportedly said that if the world is not prepared in terms of antivirals and vaccines, millions of people could die.

Osterhaus also says if the problem of vaccines is resolved, pandemic preparedness planning will be much more realistic.

Scientists say viruses continually mutate and any vaccine against a pandemic flu virus can only be designed after the disaster has occurred.

Drug companies are however already designing "pre-pandemic H5N1 vaccines" hoping they may offer a certain level of protection before a pandemic vaccine is ready.

Producing a vaccine can take up to six months and many believe the process needs to be shortened to two or three months.

It appears that while the technology exists the capacity does not; the world production of flu vaccine is 400 million doses and clearly not enough for 6 billion people plus people who could need two shots each.

The imminent threat of a pandemic has encouraged the development of new projects to make vaccines cheaper and more effective, in some cases using less antigen which stimulates the production of antibodies, and more adjuvants which enhance the effect of drugs or vaccines.

Experts emphasise the need to move away from using chicken eggs in the production of flu vaccines as the process is too slow.

Meanwhile an experimental bird flu vaccine for humans produced by GlaxoSmithKline in the UK appears to answer some worries.

The vaccine apparently offers cross-immunity against "drifted" strains of the virus, which suggests it could provide protection in the event of a pandemic.

It seems the vaccine was able to recognise and kill an Indonesia H5N1 strain that was genetically quite different from the Vietnam one included in the vaccine.

This is important because it indicates the vaccine may help the body's immune system resist future variants of H5N1 and could slow down the spread of the disease.

The vaccine contains a special adjuvant, or additive and evidence shows 77 percent of people given the vaccine with the Vietnam strain also had a strong antibody response to a separate Indonesia strain, 42 days after immunisation.

This response was seen to be 25 times greater than that in patients given a non-adjuvanted vaccine; adjuvants help boost the immune system and make it respond more efficiently.

A study with animals also found the vaccine provided 96 percent cross-protection against the drifted Indonesia virus strain.