HIV vaccine works in an investigational trial success

Originally published in MedPage Today

by Michael Smith, MedPage Today North American Correspondent

For the first time, an investigational HIV vaccine has shown it can protect people from the virus.

medpage-today In a large phase III trial, the vaccine candidate reduced the risk of infection by 31.2% compared with placebo.

The trial, conducted in more than 16,000 volunteers in Thailand, enrolled volunteers from the community, rather than high-risk groups, as many other vaccine studies have done.

In the final analysis, there were 74 infections in the placebo arm, compared with 51 in the vaccine arm.

“This is the first HIV vaccine candidate to successfully reduce the risk of HIV infection in humans,” said Lieutenant General Eric Schoomaker, the Surgeon General of the U.S. Army.

The army was one of the partners on the trial, along with the Thai Ministry of Public Health, the National Institute of Allergy and Infectious Diseases, Sanofi Pasteur, and Global Solutions for Infectious Diseases.

“We are very excited and pleased with the outcome of this trial and congratulate all those who participated in it,” Schoomaker said in a statement.

He added that the study is “an outstanding example of international and interagency collaboration.”

The trial tested a so-called “prime-boost strategy” using two different medications.

The first, dubbed ALVAC-HIV, was a canarypox virus, engineered so it could not cause disease, and modified to carry synthetic versions of three HIV genes, known as gag, env, and pro.

Volunteers were given four injections of ALVAC-HIV over six months or a matching placebo.

At the last two injections, they were also given a shot of AIDSVAX B/E (or placebo) — a vaccine candidate that had been tested on its own and found to be safe, but without benefit.

The AIDSVAX B/E contains an HIV protein known as gp120.

The idea was to prime the immune system with the first vaccine and then boost it with the second. Researchers hoped to elicit both antibodies to HIV and killer T cells that would destroy the virus.

Both medications contained HIV fragments from subtype B — common in Europe and North America — and subtype E, found in Thailand and Southeast Asia.

The trial was controversial when it started, largely because of the previous failure of the AIDSVAX component.

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