Vaccine Disappointment
posted: 21/11/2008
The progress towards an effective anti-HIV vaccine is painfully slow. The latest attempt has failed as a clinical trial shows.
The vaccine was one from the pharmaceutical company Merck, but the trial results show it offered no protection against infection by the virus.
Scientists have been trying in vain to create an effective vaccine against (HIV) for around 20 years, and some doubt that we will ever produce a working, safe anti-HIV vaccine because the virus is so evasive and rapidly evolving.
Experts described the results of the US trial, published in The Lancet, as “disappointing”.
The Step Study, led by Susan Buchbinder, from the San Francisco Department of Public Health, compared the vaccine with a non-active placebo in almost 3,000 patients.
All were free of HIV infection at the start of the trial but considered to be at “high risk” because of their lifestyles.
The study showed that the vaccine, known as MRKAd5 HIV-1 gag/pol/nef, totally failed to protect against HIV infection.
raised rates of infection?
In fact some people given the vaccine had a slightly higher rate of infection than those receiving the placebo, causing the trial to be called off prematurely in July this year.
The vaccine was designed to trigger a protective response by “killer” cytotoxic T-cells, white blood cells that are a key element of the immune system.
It had previously shown positive results when tested on monkeys exposed to a simian-HIV (SHIV) viral infection, a mixture of simian and human forms of the virus.
Dr Merlin Robb, from the US Military HIV Research Program in Rockville, Maryland, said: “The Step results have profoundly affected the HIV-vaccine development field. The failure of Step has not closed the door on the T-cell vaccine concept.”
Lisa Power, Corporate Head of Policy at the Terrence Higgins Trust charity said: “HIV vaccine development is a long term goal with many short term setbacks.
“However, it’s always disappointing when a promising avenue of inquiry turns out to be empty.”
Infection expert Professor Robin Shattock, from St George’s, University of London, said: “While the results of this trial were disappointing, this study was still an important step in determining what is required for an HIV vaccine.
“We now know that the vaccine approach tested in this trial produced a response against too few viral targets, using only one aspect of the immune response — cytotoxic T-cells.”
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