Report on the Global HIV/AIDS epidemic

Prevention: daunting challenges ahead

looking into the genetic variability of the virus, which might affect the protection a vaccine could confer.
The information that scientists generate is in turn being used by the pharmaceutical and
biotechnology industry to develop "candidate vaccines" to be tested in HIV-negative
human volunteers. The first human trial of an HIV-preventive vaccine was conducted in
1987 in the United States. Since then, more than 30 small-scale trials have been conducted, including 12 in developing countries (Brazil, China, Cuba, Thailand and
Uganda). These trials, carried out with the participation of more than 5000 healthy volunteers, have shown that the candidate vaccines are safe and that they induce immune
responses that could potentially protect people against HIV infection.
The first large-scale HIV vaccine trials, designed to show whether the candidate vaccines actually protect against HIV infection or disease, were launched in 1998 in the
United States and in 1999 in Thailand. The trials involve 8000 healthy volunteers who are
given one of two different versions of gp 120, a protein located on the outside of the
virus, depending on the virus strains prevalent in the two countries. The initial results
from these trials may be available within the next two years. In parallel, other candidate
HIV vaccines are being developed through different experimental approaches. Some are
based on the HIV strains prevalent in developing countries. Most of these newer candidate vaccines will be tested in small-scale trials in human volunteers, and the best will
proceed to large-scale evaluation for efficacy.
Vaccine development is complicated not only by the range of virus subtypes circulating
but by the wide variety of human populations who need protection and who differ, for
example, in their genetic make-up and their routes of exposure to HIV. Inevitably, different types of candidate vaccines will have to be tested against various viral subtypes in
multiple vaccine trials, conducted in both high-income and developing countries. It is
vital for developing countries to build up their technical and human capability to conduct
such trials with the highest ethical and scientific standards and with the full participation
of the community.
Most likely, the initial HIV vaccines will not be 100% effective, and they will have to be
delivered as part of a comprehensive prevention package. What is important now is to
ensure that countries where there is an urgent need for HIV vaccines participate in the
global effort to ensure that a vaccine appropriate for their use is developed. Likewise, it
is not too early to start planning how to ensure that a future vaccine is made available in
the areas of the world where it is most needed.
In Asia, a clearly defined "gay" identity is even rarer than it is in Latin America. There
is very strong social pressure on men to marry and father children, and men who
have sex with men are commonly married as well. This results in even higher levels
of potential "bridging" than those recorded in Latin America.
In one study of truck drivers in India - men who spend long hours together on the
road - almost a quarter reported oral or anal sex with a man, and all of those said.,t

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