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July 1, 2002

U.S. IMMUNIZATION NEWS

"Hope in a Vial"

Scientific American (www.sciam.com) (06/02) Vol. 286, No. 6, P. 38; Ezzell, Carol

At the beginning of the AIDS epidemic, scientists predicted that a vaccine would be discovered within two years, or by 1986; in 2000, researchers were beginning to doubt that a vaccine would ever be found.  Nearly 20 years after the AIDS panic swept across the developed world, signs are beginning to point upward again, as researchers find new pathways that have not yet been studied and abandon those that have proven unusable.  Furthermore, results from a major trial of an AIDS vaccine are due out soon, and while the data is not promising, it is the most advanced any AIDS vaccine study has become.  The U.S. government is planning a large-scaled AIDS vaccine trial in Thailand this fall, though that also faces difficulties associated with the ethics of providing a vaccine that does not confer complete immunity.  The vaccine currently under investigation, made by VaxGen, will be submitted for approval to the FDA by VaxGen if patients exhibit as little as a 30 percent lower risk of contracting HIV; public health authorities say, however, that such a vaccine could induce people to engage in riskier behavior on the assumption that they are protected against HIV, and in a high-density HIV population like Thailand anything less than a 75 percent lower risk would do little good.  Part of the problem AIDS researchers face is that there is no immune response found anywhere in nature, giving them no leads as to the structure an AIDS vaccine needs to help the body fight off HIV.  The VaxGen vaccine and the U.S.-Thai vaccine are different in the vehicle they use to reach cells and how they stimulate a response by immune system cells, while Merck is beginning to test a vaccine that is a combination of the two that will better elicit a response from the immune system over time.

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