Tests Dash Hopes Of Rapid Production Of Bird Flu Vaccine

New Scientist ^ | 12-16-2005 | Debora MacKenzie

[blam]

Tests dash hopes of rapid production of bird flu vaccine

17:43 16 December 2005
NewScientist.com news service
Debora MacKenzie

The results of first large-scale trials of a low-dose vaccine against H5N1 bird flu have been announced – and they are unexpectedly disappointing. Scientists had hoped that very low doses of vaccine virus would make humans immune if injected along with an immune-stimulating chemical called an adjuvant.

But on Thursday, French vaccine company Sanofi pasteur announced that in tests on 300 people in France, they did not. “The prospects for adequate global supplies of an effective pandemic vaccine of any kind are dimmer now than they were last week,” David Fedson, founder of the vaccine industry’s pandemic task force, told New Scientist.

The first tests of H5N1 vaccine in the US in August 2005 found that the virus on its own does not stimulate much immunity in people. To elicit enough to ward off disease, a vaccine required 90 micrograms of the virus’s main surface protein - six times more than is needed in ordinary flu vaccine.

The less virus is required per dose of vaccine, the more doses vaccine factories can produce in the limited time that will be available to immunise people at the start of a pandemic. Research with other types of bird flu have found such low-dose vaccines are possible, if the virus is combined with an adjuvant.

Antibody response

So Sanofi tested various doses of a vaccine virus based on the H5N1 that killed people in Vietnam in 2004, plus the most widely used adjuvant, alum. But no dose under 30 micrograms elicited enough antibodies to meet official standards for flu vaccines.

This means, says Fedson, that “if all the world's influenza vaccine companies were to produce this vaccine for six months, there would be enough to vaccinate only 225 million people".

“Thirty micrograms is obviously too high,” says Agnes Hoffenbach, Sanofi’s head of pandemic vaccine research. “In our next studies we will try and get lower doses to work.”

One problem may be the adjuvant. The earlier studies of other types of bird flu used one called MF59, patented by the US firm Chiron. Supplies are limited and it is not yet approved for human use in the US and some other countries.

Split virus

Another problem could be that Sanofi’s vaccine contained a split virus, rather than whole, killed virus. Split viruses are used for standard flu vaccines, as they elicit fewer side effects, but whole viruses are suspected to be more immunogenic.

China’s Sinovac company is now testing a whole-virus H5N1 vaccine with alum. Takato Odagiri, head of the flu virus lab at Japan’s National Institute of Infectious Diseases, reported at an international meeting in Malta in September that in his tests, whole-virus H5N1 vaccines seemed more immunogenic than split virus. He is now focusing his research solely on whole-virus vaccines.

But Hoffenbach told New Scientist: “I don’t think we will look at whole virus vaccines.” They would require new manufacturing processes that would have to be tested and approved. “We used our existing process because it is the fastest way to move to large-scale production.” Tests of Sanofi H5N1 vaccine planned in the US for 2006 will also use split virus.

Fedson says more avenues should be tried. “The prospects for developing a pandemic vaccine that can be produced in the quantities the world will demand are now enormously more difficult,” he says. “We have much more work to do.”

[little jeremiah]

Avian flu vaccine information.

[Rodney King]

Don't worry, this is all just a silly scare story anyway, like Ebola, West Nile, and whatever the one in China a few years ago was. Next year we will have forgotten all about it, and started worrying about a new disease.