AIDS Vaccine Success Is 'Modest'
First-Ever Protective Effect Is Small but Suggests HIV Vaccine Is Possible
Sept. 24, 2009 - "Modest" success in an HIV vaccine trial shows for the
first time that vaccination can protect people against infection with the AIDS
It's a small but significant step forward. Few, if any, think this vaccine
is effective enough to deploy in the worldwide fight against AIDS. But many
experts say it offers badly needed hope to an effort marked by many expensive
"While these results are encouraging, we recognize that further study is
required to build upon these findings," Col. Nelson Michael, director of the
U.S. Military HIV Research Program, says in a news release.
The trial was a collaboration between the U.S. Army, Thailand, the U.S.
National Institute of Allergy and Infectious Diseases, Sanofi Pasteur, and
Global Solutions for Infectious Diseases. It tested Sanofi's ALVAC vaccine
boosted with a dose of GSID's AIDSVAX.
Conducted in Thailand, it began in 2003 and enrolled 16,402 adult,
HIV-negative men and women. Half got the two-part vaccine, and half got
inactive placebo shots.
Over the course of the study, 74 placebo recipients and 51 vaccine
recipients became infected with HIV. The difference isn't large, but it
translates into 31% vaccine effectiveness. That is, it lowered the risk of
getting HIV by 31%.
That's "an important step forward in HIV vaccine research," NIAID director
and long-time AIDS researcher Anthony Fauci, MD, says in a news release.
"Certainly this is an encouraging advance."
Even so, the study results are puzzling. It was expected that vaccine
recipients who became infected would at least have some protection against the
virus. But the study found no evidence of such protection. HIV levels were just
as high in vaccine recipients who became infected as in placebo recipients who
contracted the virus.
Perhaps more importantly, the study fell far short of its goal of reducing
the risk of HIV infection by 50%.
The study was controversial from the outset. It's the largest HIV vaccine
trial yet conducted, and some AIDS activists called the study a waste of
AIDSVAX, the first HIV vaccine ever to be tested, had already failed to
prevent HIV in a number of trials. ALVAC, a live canarypox virus carrying HIV
genes, did not appear to stimulate strong immune responses in healthy people.
And similar combination vaccine strategies showed little evidence of eliciting
strong immune responses.
Moreover, a similar study of the ALVAC and AIDSVAX vaccines had been
canceled in the U.S. And critics said the study design would make it hard to
tell which part of the vaccine regimen was or was not effective.
Now that the study is completed, researchers will go over the data with a
fine-tooth comb. They'll try to figure out what worked and build on that
"Knowledge gained through this study will be used to accelerate future study
design and testing as researchers continue the search for a safe, globally
effective HIV vaccine," Col. Jerome Kim, HIV vaccines product manager for the
U.S. Army, says in a news release.