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Results of vaccine studies are mixed

By Steve Johnson
San Jose Mercury News

SAN JOSE, Calif. - Although VaxGen has received nearly $1 billion in federal contracts since 2002 to make an improved anthrax vaccine, it's not yet clear whether the vaccine will be better than the existing one, known as AVA.

VaxGen's main responsibility is to make a vaccine that is more consistently pure than AVA, according to VaxGen executives and government officials. That may result in a vaccine that is more effective, causes fewer side effects and requires only three doses, instead of the six needed with AVA. But the government isn't insisting on those improvements, they said.

Studies comparing the two vaccines so far provide a mixed picture. Both can prevent fatal anthrax infections in animals. But determining how the drugs would perform in people is more difficult.

Exposing people to a disease to test a vaccine's effectiveness is considered dangerous and unethical. So VaxGen's tests in people check to see if the drug is safe and can bolster the person's immune system, making them more resistant to anthrax.

The first of two studies VaxGen conducted in people compared VaxGen's vaccine with AVA. It found both vaccines seemed to work by triggering an immune response. But those receiving AVA had more instances of arm pain from the injections, while those taking VaxGen's vaccine were more likely to complain of mild headaches and fatigue.

It's hard to draw conclusions from that study, in part because the number of people participating, 100, was so small, said Dr. Harry Keyserling, an Emory University professor who oversaw the study.

The second test, with about 500 people, made no effort to compare VaxGen's vaccine with AVA. It measured how effective VaxGen's vaccine could be when a booster ingredient is added.

That test turned up a problem, the company reported in March 2005. Instead of improving the immune response, the booster lowered it. VaxGen executives say they have since adjusted the vaccine's formula to fix the problem. They plan to begin a third test in people this summer.

The executives said their BioShield contract also required a fourth study in people. They claim the government has also demanded that a fifth study be done, which would delay the vaccine's delivery, and postpone payments to Vaxgen.

Government officials deny adding any new study requirements.