June 2 (Bloomberg) -- An AIDS vaccine similar to one tied to higher infection rates in an earlier study may soon be tested in about 3,000 people by U.S. scientists.

Government advisers voted 23 to 3 on May 30 in favor of the new study, and Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, said he would review their comments and decide ``reasonably soon'' whether to proceed. The government-developed vaccine has components similar to those in a shot made by Merck & Co. that was terminated last year when 49 recipients became infected, compared with 33 people who got sham inoculations.

Panel members who backed the government's test said it may yield valuable data about vaccines that rely on the action of immune system cells. The study was reduced in size by about 50 percent after Merck's test failed in September, and the International AIDS Vaccine Initiative, a research and advocacy group that has helped bring six vaccines to human testing, said it wouldn't participate in the government product's test.

``If this trial goes forward, it will be the most complicated AIDS vaccine trial that any of us will ever have to explain,'' said Mitchell Warren, executive director of the AIDS Vaccine Advocacy Coalition, a non-profit New York-based advocacy group, and a supporter of the trial. ``We have a massive undertaking ahead of us.''

The failure of Whitehouse Station, New Jersey-based Merck's vaccine, called Ad5 because it contained a so-called adenovirus, a cold-causing germ, spurred researchers to pursue new ways to defeat the lethal disease that now infects more than 33 million people. The vaccine is composed of genes from HIV combined with the adenovirus.

Men at Highest Risk

All but one of the infections in the Merck trial struck men. Merck has said that uncircumcised men and those with high levels of immunity to the adenovirus before getting Ad5 were at highest risk of catching HIV, the virus that causes AIDS.

Since the Merck result, no vaccine is expected to have a chance of gaining approval for at least 10 years, including the government's vaccine. The global cost of preventing, treating and fighting AIDS may reach $18 billion next year, according to the Global Fund to Fight AIDS, Tuberculosis and Malaria.

For safety reasons, trials on the U.S. vaccine, called VRC after the government's Bethesda, Maryland-based Vaccine Research Center where it was developed, will include only circumcised men with no immunity to the adenovirus, said Scott Hammer, a Columbia University infectious disease specialist who heads a group designing the trial.

Hints of Protection

Some results from the Merck trial that were presented at the meeting hinted a vaccine that is like VRC might offer some protection against HIV, said Jerald Sadoff, a former Merck vaccine scientist who now heads the Aereas Global TB Vaccine Foundation, a Washington-based non-profit group developing an affordable tuberculosis vaccine.

Juliana McElrath, a panel member from the University of Washington, in Seattle, presented a follow-up analysis of some Merck vaccinated subjects who, although infected, had relatively low levels of HIV in their blood.

All these patients had responded strongly to one component of the Merck vaccine, an HIV protein called ``gag,'' said McElrath, who is also laboratory director for the HIV Vaccine Trials Network, a group of medical clinics that participate in human tests.

``In my experience with developing vaccines, if you get a clue in humans, you focus everything on it,'' Sadoff said in support of the test at the panel meeting.

Data `Unclear'

Merck spokeswoman Mary Elizabeth Blake said the significance of the data from its trial, called STEP, is ``unclear.''

``We continue to analyze the results of STEP to inform the continuing search for an effective HIV vaccine,'' Blake said in an e-mail yesterday.

Researchers against the VRC trial said that, since it is no longer a test of a shot that may be widely used, it should be considered to make sure it provides maximum information.

``We're redesigning the aims of human HIV vaccine research without redesigning the vaccine,'' said Dennis Burton, an immunologist at Scripps Research Institute in La Jolla, California, who was added to the panel at the meeting. ``Let's not go into a human experiment without a clear idea of what we're going to learn.''

Enid Moore, a Seattle-based community relations expert with the HIV Vaccine Trials Network, said people at risk of the disease are ready to enroll.

However, Martin Delaney, founder of the San Francisco-based AIDS patient advocacy and education group Project Inform, said the evidence of potential benefit from Ad5 was too faint, and the risks too great, to go forward.

``This is one particular trial that's going to answer some rather obscure questions that aren't going to give us an AIDS vaccine any time soon,'' he told the panel. ``We ought to consider the bigger picture.''

To contact the reporter on this story: John Lauerman in Boston at jlauerman@bloomberg.net.

Last Updated: June 2, 2008 00:00 EDT