Preventive HIV Vaccines
Though several studies are completed or underway, we are years away from an effective preventive HIV vaccine. These studies recruit people who are HIV-negative. The vaccines are being evaluated first for their safety and ability to induce an immune response (in Phase I and Phase II studies) and later for their ability to prevent the establishment of HIV infection and/or disease (in Phase III studies).
There are 5 mid-sized and nearly 30 small studies of other experimental preventive HIV vaccine candidates ongoing. Several products and combinations of products are being evaluated for safety and their ability to promote immune responses.
Results from the first large study to evaluate the effectiveness of a vaccine, called AIDSVax, showed that it did not work. HIV infection rates were similar among those who received vaccine and placebo, meaning that receiving the vaccine did not protect people from HIV infection.
Who Participates in Preventive HIV Vaccine Studies?
Small studies of HIV vaccines typically include HIV-negative people who are at very low risk for HIV infection. Mid-sized studies typically include HIV-negative people who are at higher risk for HIV infection. Large studies include HIV-negative people who are at very high risk for HIV infection (such as current injection drug users and sex workers).
Why Do Large Studies Only Include People at Very High Risk for HIV Infection?
Large studies target people at very high risk for HIV infection in communities with known HIV infection rates. Certainly, this doesnt mean other groups aren't at risk -- everyone is at risk for HIV infection. However, researchers can get better data on infection rates among groups where infection rates are known to be high. The higher the number of infections in a given population, the fewer people needed in a study to determine if a vaccine works.
Are There Side Effects of Experimental Preventive HIV Vaccines?
Each product will carry its own unique risk of side effects. In general, however, side effects associated with experimental preventive HIV vaccines have been similar to side effects of commonly available vaccines: redness, swelling and/or pain at the site of the injection and sometimes mild flu-like symptoms. Side effects could be more severe than mild pain or flu symptoms, however. They could include more severe pain and/or ulceration at the site of injection.
If the vaccine was made out of whole-killed or live-crippled HIV, then it's possible there could be a risk of HIV infection from the vaccine itself. However, that there have been no studies of whole-killed or live-crippled preventive HIV vaccines in the United States.
Are There Other Risks of Participating in a Preventive Vaccine Study?
It is possible that receiving an experimental preventive HIV vaccine could increase the likelihood of HIV infection should someone become naturally exposed to HIV.
It is possible that if someone received an experimental preventive HIV vaccine and became infected with HIV (because the vaccine didn't work) that the vaccine could increase the rate of HIV disease progression.
It is also possible that an experimental preventive HIV vaccine could cause a later effective preventive HIV vaccine not to work. It is very likely that people who participate in a study of a preventive HIV vaccine and receive the experimental vaccine (as opposed to the placebo) will not be eligible to participate in studies of other preventive HIV vaccines and other HIV prevention approaches (like microbicides studies).
Are There Possible Benefits to Participating in These Studies?
The most important benefit to participating in these studies is the benefit to community and science, called altruism. Whether or not a vaccine succeeds or fails, if the experiment is well designed, the results bring us one step closer to an effective preventive HIV vaccine. Getting closer to an effective HIV prevention is an important benefit to us and future generations.
It is possible, by participating in an experimental preventive HIV vaccine study, that the vaccine will be effective. Participants who received the vaccine (as opposed to the placebo) will have gained earlier access to an effective preventive HIV vaccine. It is also possible that an experimental preventive HIV vaccine will not prevent HIV infection, but may prevent HIV disease progression among those who do become infected with HIV. While these outcomes are theoretically possible, it is vital to remember before entering a trial that they are merely that -- theory.
Ultimately the decision to participate in a study of an experimental preventive HIV vaccine is a personal decision. It's important to remember that the very fact that an HIV vaccine is being researched means that we don't know if it works. The worst outcome of these studies may be that people believe that they're getting an effective product, increase HIV risk behaviors and increase HIV infection rates overall among study participants. The best outcome is that we move toward identifying an effective HIV preventive vaccine.
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