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Tuesday 25th October 2016

Merck halts AIDS vaccine trial

24th September 2007

International pharmaceutical giant Merck & Co has announced it will terminate trials of its AIDS vaccine, which it had been developing for a decade, because it failed to prevent HIV infection in volunteers.


The trials were halted after it was found that those who had been innoculated with the trial vaccine were showing a higher incidence of infection than a control group. Volunteers were from groups thought to be at a high risk of contracting HIV.

Merck was co-sponsoring the trial with the HIV Vaccine Trials Network, which gets its funding from the National Institute of Allergy and Infectious Diseases under the US National Institutes of Health.

The trial, codenamed STEP, enrolled 3,000 volunteers in the trial, a large proportion of whom were from high-risk groups like gay men or female sex workers in multiple locations including North and South America, the Caribbean and Australia. An additional trial was held in South Africa.

Experts were surprised at the abysmal results, citing good immune responses produced in earlier trials.

The vaccine was made up from a common cold virus, upon which three synthetically produced genes from the HIV virus were superimposed.

It had been hoped that the synthetic genes would stimulate the body's T-cells to give a higher degree of protection against HIV, as a strong T-cell response has been associated with a better prognosis among those already infected with HIV.

However, out of 741 volunteers who received the vaccine, 24 became infected with HIV, while in the 762 volunteers who received a placebo, 21 cases of HIV infection were reported.

Neither did the vaccine appear to give any benefit to those who became infected.

Volunteers in both groups were given repeated information about safer sex practices, Merck said in a statement.

Peter S Kim, president of Merck Research Laboratories, said the company would study the data closely and share it with the scientific community so as to inform the ongoing global search for an AIDS vaccine.



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