::What it is
:: Why it is Important
:: How it is Done
What it is
Vaccines stimulate the body’s immune system to provide protection against infection or disease. Vaccines against HIV are being developed, and they are in various stages of clinical trial but at present none have proven effective.
Why it is Important
It is important to conduct research to find an effective vaccine because:
- The availability of a safe, highly effective and accessible preventive HIV vaccine would be a valuable complement to other preventive interventions, significantly contributing to the interruption of the chain of transmission of HIV.
- Well conceived HIV immunization strategies could reach populations where other interventions are not sufficiently effective.
- Research on preventive HIV vaccines is providing new information on the possible use of vaccines as therapeutic interventions, to be used in association with antitretroviral therapies, which could lead to a lowering in the cost of the treatments and to an increase on their long-term efficacy.
How it is Done
Vaccine research is a long process that begins with basic laboratory research and product development, including animal experiments, mostly performed in academic laboratories and by the pharmaceutical industry.
The next step is to test these products (candidate vaccines) on healthy human volunteers through sequential phases. Phase I and II trials provide data on the safety of the candidate vaccines and on their ability to induce immune responses specific to HIV. These trials are done among small numbers of volunteers (50-200 per trial). Depending of the results obtained, candidate vaccines can proceed to large-scale Phase III trials, to obtain definitive information about their efficacy in inducing protection against HIV infection or AIDS. For scientific reasons, Phase III trials are done in populations with a high incidence of HIV infection, involving thousands of volunteers.
Since 1987, more than 30 HIV candidate vaccines have been tested in approximately 60 Phase I/II trails, involving more than 10,000 healthy volunteers. Most of these trials have been conducted in the United States and Europe, but several have also been
conducted in developing countries (Brazil, China, Cuba, Haiti, Kenya, Peru, Thailand,
Trinidad, and Uganda). The results have confirmed the safety of the vaccines, and have provided important scientific information to develop newer generations of candidate vaccines with better ability to induce anti-HIV specific immune responses.
At the present time, there are only two related candidate vaccines being evaluated in Phase III efficacy trials. The first trial started in 1998 in the United States (with sites in Canada and the Netherlands), enrolling 5,400 volunteers, mostly homosexual men. The trial is evaluating the efficacy of an envelope gp120 candidate vaccine based on the HIV subtype circulating in North America (subtype B), and the definitive results will be available early in 2003. The second Phase III trial started in 1999 in Thailand, and is testing the efficacy of a gp120 candidate vaccine based on the subtypes B and E prevalent in Thailand, enrolling a total of 2,500 volunteers, the majority of which are recovering intravenous drug users. Results from this trial will be available late in 2003.
The “simultaneous” development and evaluation of multiple vaccine concepts require that vaccine evaluation “sites” are identified and strengthened in multiple developing countries. This process requires intense national, regional and international coordination and collaboration. An example is the WHO-UNAIDS driven “African AIDS Vaccine Programme (AAVP)”, a network of African experts working to facilitate the development and evaluation of AIDS vaccines for Africa through regional and international collaboration and capacity building (from ethics to clinical science).
Strategies must also be put in place to ensure that once an HIV vaccine is discovered, delivery systems are in place so that it can be made available without unnecessary delay to all people in need.
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The global investment on HIV vaccine research, including industry and research agencies in industrialized countries has been estimated at approximately US$ 500 million per year. A very small fraction of that amount is dedicated to the activities aimed at developing vaccines for developing countries.
This level of investment is insufficient to carry on the simultaneous development of multiple vaccine products in parallel. Investments in HIV vaccines must be increased, including significantly higher budgets to build capacity in developing countries to conduct trials. As an example, initial budget estimates for the AAVP are in the order of US$ 25 to 35 million per year, just to complement other ongoing research efforts by other organizations.
In addition to its activities in Africa, the WHO-UNAIDS HIV Vaccine Initiative is also collaborating with national authorities and scientists working with HIV vaccine development and evaluation in other continents.
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