HIV Vaccine Shows Modest Results, Instills Hope for More Effective Vaccine

(Sept. 24) For the first time in the history of HIV research and prevention researchers have found a vaccine regime that has shown modest results in the prevention of HIV infection.

The trial found that those receiving the prime-boost vaccine were 31% less likely to become infected with HIV than those receiving the placebo.

“These new findings represent an important step forward in HIV vaccine research,” says Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID). “For the first time, an investigational HIV vaccine has demonstrated some ability to prevent HIV infection among vaccinated individuals.”

The prime-boost regimen was a combination of two vaccines: ALVAC-HIV vaccine (the primer dose) and AIDSVAX B/E vaccine (the booster dose). The vaccines are based on the subtype B and E HIV strains that commonly circulate in Thailand. The subtype B HIV strain is the one most commonly found in the United States.

The Thai Phase III HIV vaccine study, also known as RV144, opened in October 2003.  More than 16,000 men and women between the ages of 18 and 30 were enrolled in the study.  They were all HIV-negative at the start of the trial.

51 people in the groups receiving the vaccine eventually contracted HIV, while 74 in the placebo group became infected.

While yielding a modest efficacy, the vaccine has encouraged hope of a more effective vaccine that would cross the 50% efficacy threshold.

“Additional research is needed to better understand how this vaccine regimen reduced the risk of HIV infection, but certainly this is an encouraging advance for the HIV vaccine field.” Dr. Fauci adds.
The vaccine regimen had no effect, however, on the amount of virus in the blood of volunteers who acquired HIV infection during the study.  Suggesting that the vaccine would not be effective in those already infected with HIV.

Previous attempts at developing a vaccine have failed, sometimes with disastrous results.

Merck stopped their study in 2007 after finding that it did not prevent infection.  Analysis of data later suggested that the vaccine may have increased the risk of HIV infection.

AIDSVAX, the booster in this study, failed in two large trials.  It was the first late stage tests of any AIDS vaccine at the time.

Researchers will announce details of their initial findings in October at the AIDS Vaccine Conference in Paris, France.

The study was sponsored by the U.S. Army in collaboration with NIAID, Sanofi Pasteur and GSID.