"The challenges in the development of an HIV vaccine are unprecedented, and the ability to induce HIV-specific immune responses does not necessarily indicate that a vaccine will protect humans from HIV infection".
The experimental HIV-1 vaccine is one of five that have progressed to tests of effectiveness in humans.
Comparatively, the new HIV vaccine yielded better immunization rate and virtually no side effects.
Shown to be safe in humans, the candidate vaccine has now advanced to the next phase of the pre-approval trial process, and will be tested in 2,600 women in southern Africa to see whether it prevents HIV infection. "Obviously, the search for an HIV vaccine is very elusive", said Dr. Carlos del Rio, who was not involved with the study but has done similar research as the co-principal investigator of the Emory-CDC HIV Clinical Trials Unit. del Rio spoke with CNN about the vaccine.
It is hoped the new vaccine would offer much better protection against the nearly unlimited number of HIV strains found across the world.
The new vaccine was tested in 393 healthy people considered at low risk for infection and 72 rhesus monkeys. The resulting vaccine, the scientists hoped, would trigger an immune response against wide range of strains of the virus.
A vaccine is a vital weapon in the war against the virus, which infects an 1.8 million people each year.
The research published in the journal The Lancet shows that the experimental vaccine generated robust immune responses.
With an estimated 1.8 million new cases of HIV every year, a safe and effective vaccine would be an incredible tool in stopping the pandemic.
For the prime vaccine, used to stimulate an initial immune response, participants were injected with Ad26.Mos.HIV, which uses a strain of the common-cold virus. Thus, an HIV vaccine is needed badly.
"How do we make a vaccine that raises immune expenses relevant for all the HIV sequences?" said Barouch.
The vaccine improved the immune responses against HIV during a clinical trial involving almost 40 healthy adults.
They say it also protected two-thirds of monkeys against an HIV-like virus. The participants were randomly assigned one of seven combinations of a vaccine, while one group was given a placebo.
The same vaccine was also tested on rhesus monkeys and proved to be partially effective, protecting 67 percent of the test subjects from simian-human immunodeficiency virus, a virus similar to HIV.
The study selected participants from around the world, notably those from the United States, Thailand, South Africa, Uganda, and Rwanda.
"We're cautiously optimistic but we need to be cautious in our interpretation of the data", Barouch told Newsweek. "We don't know whether protection in monkeys means there will be protection in humans".