Why do HIV Vaccine Trials keep Failing?

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Why do HIV Vaccine Trials keep Failing

HIV is considered as a challenge for a vaccine. Scientists have been working on getting a vaccine for a very long time. As known, this virus was the cause of AIDS. HIV is an organism considered as extremely difficult to get vaccinated against.

This organism reproduces very rapidly and also in an imperfect manner. This means it becomes resistant to the vaccine’s created immune defenses. This also becomes drug-resistant equally fast.

HIV is known to hijack the cellular immune response of the body and use the T-cells directing that response as the breeding ground. This means, most of the basic vaccines, that use the weakened but live versions of the infection can cause the infection. This is a retrovirus. This means it can hide away inside the genetic code of an individual deeply. The virus is invisible to the immune system.

Considering the above factors, it means there is no immune response naturally that is strong enough to contain or even prevent the infection. HIV is a life-time virus and needs therapy for life.

The Search for a Vaccine:

The first two trials for efficacy were launched in the year 1998. This was called ‘Vax’. Almost 8000 people were enrolled for this in Thailand, Netherlands, Canada, and the US. The strategy used here was the same strategy that is always used in most of the trials for efficacy. This is the ‘prime-boost’ strategy that consists of 2 vaccines.

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This ‘Vax’ trial was unsuccessful and ended in the year 2003. The AIDSVAX, a component of the HIV-protein is used in other trials.

In December 2004, a key study, HVTN 502 or STEP started enrolling around 3000 people. This was solely a vector vaccine trial. The shell of the ‘vector’ was based on adenovirus. This is a virus that causes an illness similar to the cold. The reaction produced by this seemed promising and there was a positive feeling that this might work.

It was a set-back when this trial of STEP was terminated in 2007, March. To add to the problem, there were more infections in those who received the vaccination.

This was no random result. Scientists conducted a study and found out that the exposure previously to the adenovirus, used as the vector of the vaccine made the cells of the people receptive to HIV infection instead of lessening this.

Two other trials for efficacy, Phambili, and PAVE, were also terminated.

Dr. Fauci says it is essential to get a vaccine to put an end to the epidemic of HIV in Sub-Saharan Africa. This is a solution for the long-term but presently no one has the required knowledge to merit large-scale, highly expensive clinical trials.

At this point in time, small scale trials work out appropriate. These can be scaled up once they have shown promising results.

Till this time, infected and vulnerable people need a different type of support, like treatment and also education. Only time will tell how the HIV vaccine can be got.