It's a tantalizing idea that scientists at George Mason University are studying. Early findings are very preliminary and based on lab tests of a small number of blood samples.
Other AIDS researchers caution against putting too much faith in such early tests, and the George Mason study has not been published in a peer-reviewed scientific journal that is standard for major medical breakthroughs.
But Ken Alibek, director of the university's National Center for Biodefense, said the early results are encouraging.
"This could result in some very important work," said Alibek, a former top scientist in the Soviet biological weapons program who came to the United States in 1992. If early results bear out, "this could be a great way to protect people," he said, because the vaccine has been safety-tested, is already in production and has been used successfully on a global scale to eradicate smallpox.
The research was based on a hypothesis that the spread of HIV in central Africa coincided with the decline of smallpox. As smallpox was eliminated and people stopped receiving vaccinations in the early 1980s, the AIDS virus began to spread rapidly.
Alibek said Raymond Weinstein, a fellow researcher at George Mason, approached him with the hypothesis.
"My first reaction was this sounds like some kind of crazy idea. But after some analysis, I realized maybe this is not so crazy," Alibek said.
To test the theory, Alibek and Weinstein studied blood samples from 10 people who received the smallpox vaccination and 10 who did not.
When HIV was introduced into the blood samples of those who had been vaccinated, the virus either failed to grow or its growth was slowed considerably. The study results were statistically significant despite the small sample size, Alibek said.
Wayne Koff, senior vice president for research and development at the International AIDS Vaccine Initiative, expressed caution about drawing too many conclusions from such early research.
He also said that pox viruses, like the one used in the smallpox vaccine, have been shown to have a general antiviral effect, but that doesn't necessarily mean they will be effective specifically against the AIDS virus.
"It's preliminary. It's intriguing. But it reminds me of a lot of the data sets we get that are preliminary and intriguing" but don't always pan out, Koff said.
Koff also was skeptical about the hypothesis that the emergence of AIDS in Africa had any connection with the decline of smallpox.
Alibek acknowledged that the research so far cannot tell if the smallpox vaccine produces a response that is specific to the AIDS virus, but on a certain level, he said, it's irrelevant.
"For a person who would be protected, it would not matter if it is specific to HIV" as long as it provides protection, he said.
Based on the research, George Mason University has filed patent applications on the smallpox vaccine's therapeutic use against HIV and AIDS.
Scientists declared smallpox eradicated in 1980, and the widespread vaccination program that contributed to its demise ended. In the early 1980s, the AIDS virus began its rapid spread through central Africa.
Concerns over bioterrorism have prompted federal officials to recommend smallpox vaccines for public health workers. More than 38,000 health-care workers nationwide have received the vaccine in recent months, though fears about the vaccine's side effects have stopped some from getting the shot.
By Matthew Barakat