Why the Thai HIV Vax Trial Worked

New molecular analyses yield clues to the success of a 2009 human HIV vaccine study.

Bob Grant
Bob Grant
Sep 19, 2011

Vaccine administrationWIKIMEDIA, US GOVERNMENT

The immunoglobulin G (IgG) antibody was key to the first-ever successful HIV vaccine trial in humans, reported researchers following up on the study's results.

In 2009, trial organizers announced that the particular vaccine combination used made people who received it 30 percent less likely to contract HIV than those who got a placebo. Since then, researchers have been pouring over blood samples from participants, hoping to determine the keys to the vaccine's marginal success where so many others have failed. Last week’s announcement marks one of the first answers to that question: individuals with the IgG antibody, which recognizes a specific part of HIV's envelope, were 43 percent less likely to contract the virus.

Knowing more about why the vaccine lent some protection against the virus may inform future efforts to create even more effective shots, perhaps targeting IgG production as a central strategy. "What we now have are clues as to why it might have worked," study leader researcher Barton Haynes of the Duke Human Vaccine Institute said at the press conference last week. "That's something we haven't had over the past 30 years. That's very important for the field."