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HIV Vaccine Pair Shows Promise

A study showing that a pair of experimental vaccines have blocked HIV infection in humans for the first time has rekindled hopes of taming the AIDS virus after decades of setbacks, researchers said Thursday.

The U.S.-funded study involving more than 16,000 volunteers in Thailand found that pairing the vaccines reduced the number of infections by 31%, a moderate performance that researchers say may point the way to vaccines reliable enough for widespread use.

"The study represents a major scientific achievement," says Lt. Gen. Eric Schoomaker, U.S. Army surgeon general, a trial sponsor. "Although the level of protection is modest," he says, the study represents a "first ever" success in humans of a research effort that has been a global health priority since HIV was discovered in the mid-1980s.

Two years ago, the vaccine effort suffered a major blow when a Merck&Co. vaccine not only failed to guard against HIV but increased infection risk. The trial was abruptly halted.

"It's almost two years to the day when that data came out," says Mitchell Warren of the AIDS Vaccine Advocacy Coalition, adding it prompted many to say of an AIDS vaccine: "Not in my lifetime."

The new finding is a welcome surprise, Warren says. "It doesn't mean we can license and distribute and vaccinate . . . but it does mean a vaccine is possible."

The $100 million, Thai-led trial started in 2003, Schoomaker says. It used vaccines that failed earlier tests: ALVAC, by Sanofi-Aventis, and VaxGen's AIDSVAX. They were made with two strains of HIV, B and E, both common in Thailand. Type B is also found in the USA. Type C predominates in Africa.

Volunteers were men and women ages 18 to 30. Fifty-one of those given vaccine became infected, compared with 74 given a placebo.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, another trial sponsor, expresses "cautious optimism" that scientists someday will be able to make a vaccine that protects against HIV.

But daunting questions remain, Fauci says, including how these vaccines work. "It's humbling how little we know," he says.

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