About The Study

This study determined whether injections of the artificial protein rgp160 (VaxSyn) would strengthen the body’s reaction against HIV in people already infected. It aimed to show if the vaccine would affect markers of disease progression (such as CD4 counts). It was not designed to show specific clinical benefits (like frequency of AIDS-related illness), because study participants would have had to be followed for many more years.

Study Approach

This study was double-blinded (neither doctors nor volunteers knew which therapy volunteers received). Participants were injected with either VaxSyn or a placebo (fake shot) over a two-year period. At the beginning of the third year, all participants were given VaxSyn.

Study population

Two hundred and seventy-eight HIV-positive volunteers were enrolled across Canada. They were relatively healthy with CD4 counts above 500.


No significant differences were observed between the treatment and placebo groups in the rate of CD4 cell decreases, the time to beginning antiretroviral therapy, the development of AIDS-related infections, the amount of virus, or the ability of the virus to infect other cells. The VaxSyn-treated group lost an average of 72 CD4 cells per year while the placebo group lost 69 cells per year. Changes in viral load from the beginning to the three-year mark were similar in both the VaxSyn and placebo groups. So far, there is no evidence that the group treated with VaxSyn experienced any change in the progress of their disease. Average CD4 counts declined at similar rates in both groups over the two-year follow-up period. This trend continues into the third year of follow-up.


This study showed no clinical benefit of the vaccine, nor did rgp160 maintain the participants’ immune systems. The results of this trial have allowed researchers to re-focus their efforts on newer AIDS immune-based therapies that are now starting to show promise.