NEW YORK (CNN/Money) - The decades-long search for an AIDS vaccine grew longer Monday when VaxGen released disappointing test results for a much-anticipated HIV inoculation.

VaxGen said trials of AIDSVAX did not cut HIV infection rates in whites and Hispanics. The setback in the fight against a virus infecting 42 million people worldwide was also a shock to investors. Shares of VaxGen fell 47 percent Monday.

The news shifts the focus of any AIDS vaccine to Merck & Co. (MRK: Research, Estimates), GlaxoSmithKline (GSK: Research, Estimates), Aventis (AVE: Research, Estimates) and a handful of university laboratories. The three drugmakers are working on early-stage vaccines for a virus that has killed 28 million people since its appearance in the early 1980s. But the availability of those inoculations could be years away.

VaxGen (VXGN: Research, Estimates) said the vaccine did seem to shield the blacks and Asians who volunteered for the 5,009-person study. But while the Brisbane, Calif.-based company called that finding "statistically significant," it also said that the sample size of those two minority groups -- 498 -- was "relatively small."

"The news on VaxGen's AIDSVAX is disappointing, but we are not discouraged," Dr. Seth Berkley, M.D., president and CEO of the International AIDS Vaccine Initiative, said in a statement. "The search for an AIDS vaccine will -- and must -- go on."

VaxGen, an unprofitable company also working on vaccines for smallpox and anthrax, said more studies will be conducted in coming weeks to clarify the data. The company also reiterated that it is conducting another late stage, or Phase III, trial in Thailand. But that wasn't enough to keep VaxGen stocks from falling $6.13 to $6.89 on Monday.

More than 14 million VaxGen shares changed hands, up from an average daily trading volume of 659,000.

Dr. Robert C. Gallo, director of the Institute of Human Virology, said he was not surprised by the vaccine's apparent failure, in part because its antibody-generating capacity comes only from a protein found in HIV.

"This is not a program that is based on solid science," Gallo said.

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While there's no cure for AIDS, a series of drugs exist to control it among those infected with HIV. One promising drug, Fuzeon, will be available for $20,570 a year, drugmaker Roche said Monday.

That lofty price tag troubled AIDS advocates who point out that the disease is most prevalent in poor countries. Of the 42 million people infected with HIV, close to 30 million live in sub-Saharan Africa, according to data from UNAIDS and the World Health Organization.

Education, abstinence and contraception remain the means of preventing the spread of the virus. Beyond that, one of the major challenges those in HIV vaccine development are dealing with is the multiple subtypes of HIV, the World Health Organization says.

The vaccine used in this trial was designed to reduce susceptibility to infection with HIV subtype B, which is common in the Americas, Western Europe, Australia, and New Zealand. But the WHO says that 11 subtypes of HIV-1 have been identified.

In its release Monday, VaxGen focused on findings showing the apparent effectiveness of AIDSVAX in black and Asian volunteers.

"This is the first time we have specific numbers to suggest that a vaccine has prevented HIV infection in humans," said Phillip Berman, VaxGen's senior vice president of research and development, in a statement. "We're not sure yet why certain groups have a better immune response, but these preliminary results indicate that a surface-protein vaccine that stimulates neutralizing antibodies correlates with prevention of infection."

Since August, VaxGen's shares had gained about 160 percent on optimism the AIDS vaccine would prove effective. But the company has been losing money. VaxGen lost $31.7 million last year on $1.6 million in sales.