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Low-Dose Bird Flu Vaccine in the Works

New Techniques May Stretch Vaccine Supply if Bird Flu Hits
By
WebMD Health News
Reviewed by Louise Chang, MD

July 26, 2006 -- An immune-boosting substance makes bird flubird flu vaccine work at low doses, drug maker GlaxoSmithKline today announced.

A 400-person clinical trial in Belgium shows that the immune-boosting substance -- what scientists call an adjuvant -- makes low-dose bird fluflu vaccine work.

The vaccine targets the H5N1 bird flu that has killed 134 people in nine countries. However, the virus has not yet learned to spread easily from person to person -- an event that likely would trigger a worldwide pandemic.

GlaxoSmithKline says that two 3.8-microgram doses of the vaccine stimulate antibody levels expected to protect people from bird flu. Without adjuvant, similar bird-flu vaccines require two 90-microgram doses.

"These excellent clinical trial results represent a significant breakthrough in the development of our pandemic flu vaccine," GlaxoSmithKline CEO J.P. Garnier said, in a news release. "This is the first time such a low dose of H5N1 antigen has been able to stimulate this level of strong immune response."

Aside from its use of a proprietary adjuvant, the GlaxoSmithKline's bird flu vaccine is similar to others now being tested. The bird flu component of the vaccine must be grown in hens' eggs using the technology now used to make seasonal flu vaccine. And people will need two doses of the vaccine, weeks apart, before they are protected. GlaxoSmithKline is a WebMD sponsor.

There is no guarantee that the vaccine now being developed will protect against a strain of bird flu that becomes able to spread among humans. If there were little protection, there would be a delay of many months in producing a vaccine against the new strain. A low-dose vaccine would greatly speed this process.

Immunologist David Topham, PhD, is testing different experimental bird flu vaccines at the University of Rochester, New York.

"This is a great result, getting a protective level of response at such low vaccine doses," Topham tells WebMD. "What this says, in the larger picture, is that using an adjuvant works for these vaccines that are not very immunogenic on their own. This is the way we will have to go in the future."

Another drug company, Chiron, is also testing an adjuvant-boosted bird flu vaccine. Early results, Topham says, suggest that Chiron's adjuvant also allows for low-dose vaccination.

One problem with adjuvants is that, because they boost the immune system, they boost the side effects of vaccination.

"The full safety profiles for these adjuvants have not been done," Topham says. "But in a pandemic situation, some of these things might be relaxed. The risk of bird flu might be worse than the risk of the side effects of adjuvants."

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