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Wanted: Volunteers to test an experimental new AIDS vaccine that is needle-free. The catch? You have to be willing to stay locked up in your room for 12 days.

The new vaccine comes in a capsule and it’s made using a common cold virus called an adenovirus, genetically engineered with a tiny piece of the AIDS virus.

It’s only a very early stage experiment, meant to show the vaccine is safe. However, if it is, it could be a start not only towards a much-needed vaccine against the AIDS virus, but needle-free vaccines against many different infections.

Researchers at the University of Rochester Medical Center are testing it in their specially designed facility usually used to test live influenza vaccines. The trial, which started Tuesday, is being paid for by the Bill & Melinda Gates Foundation.

“We’ve had success doing this before. The facility is very nice,” says Dr. John Treanor, a vaccine expert at Rochester who’s helping lead the study.

“We try and make sure they eat well and they are entertained. But they do have to stay in there for the 12 days.”

“We have a strong suspicion that it is going to be safe."

The reason is that the adenovirus used to make the vaccine is “alive” – it can replicate and presumably will spread in the digestive tract. Tests in monkeys show it should be safe, but the researchers are taking extra care because this particular strain, called adenovirus 26, only lives well in humans.

It’s been severely weakened, but so-called live vaccines tend to prompt a stronger immune response than “killed” vaccines.

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“We have a strong suspicion that it is going to be safe. It is an attenuated virus,” said Dr. Dan Barouch of Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, who helped design the vaccine. A similar oral vaccine has been given to hundreds of thousands of young military recruits to protect them against two other common old viruses – adenovirus 4 and 7 – that can cause severe outbreaks on bases.

And scientists hope that using the oral route will activate the immune system via the digestive tract – something that’s worked well before with, for instance, polio virus.

Making an AIDS vaccine has been one of the hardest problems facing medical science. The human immunodeficiency virus (HIV) that causes AIDS has infected nearly 78 million people. About 39 million have died, according to the World Health Organization.

In the United States, more than 1.2 million people have HIV, and about 50,000 people are newly infected each year. Medications can keep infected people healthy, but there is no cure. Some of the same drugs can also protect people against infection but they must be taken daily, unlike a vaccine.

Doctors have been working to make a vaccine against HIV for decades, but while they’ve had partial successes, nothing has worked as well as vaccines against measles or smallpox.

It’s partly because HIV attacks the very immune cells that are usually mobilized by a vaccine, and partly because the virus cloaks itself in an ever-changing envelope.

The new vaccine was designed using a computer program that’s picked out a batch of these envelope protein disguises from HIV around the world. The hope is that it will help the immune system recognize and respond to a range of disguised HIV proteins.

As the harmless adenovirus spreads, it should activate an immune response. The immune system cells will also "see" the attached bit of HIV and, the researchers hope, react against any HIV virus should the vaccinated person ever be exposed.

"An oral vaccine would be highly desirable, particularly in the developing world."

Other vaccines have been made against HIV using killed adenovirus. They haven’t worked too well. Barouch hopes that using a live one will work better.

Another reason vaccines made using adenoviruses have not always worked well is because the viruses are so common. People already often have an immune response to them, so the vaccines don’t have time to take hold in the body.

Adenovirus 26, however, is very rare, Treanor says. “It’s an unusual serotype of human adenovirus,” he told NBC News. It has only infected about 5 percent of the population, he said, and doesn’t make people sick. “It does not appear to be associated with any detectable symptoms,” he said.

That suggests the vaccine, if it protects against HIV, could be widely deployed.

And if the capsule form works, so much the better. “On a practical basis, an oral vaccine would be highly desirable, particularly in the developing world,” Treanor said.

And Barouch says there’s no reason a similar vaccine design couldn’t be used to make immunizations-in-a-pill against a range of bacteria and viruses.