A potent vaccine  may reduce HIV to a minor chronic infection, similar to the herpes virus, Spanish researchers said Wednesday. But experts warn that a cure for HIV/AIDS is still a long way away.

Professor Mariano Esteban, of the Spanish Superior Scientific Research Council, tested the vaccine, known as MVA-B, on 24 healthy patients. Ninety percent of the participants who received the vaccine developed an immunological response to the virus, and 85 percent of them still had the response after one year of receiving the vaccine.

“MVA-B vaccine has proven to be as powerful as any other vaccine currently being studied, or even more,” Esteban said in a statement.

The vaccine contained four HIV genes that stimulated two types of white blood cells to attack and destroy the sickly HIV cells. Nearly 75 percent of the study participants developed HIV-specific antibodies to protect against the virus.

Next, Esteban and colleagues plan to test the vaccine in people who suffer from HIV in order to see whether the injection has therapeutic qualities.   But experts, including Esteban, noted that an antibody response is not full protection, and much more research must be underway.

“The biggest problem with vaccine trials is unlocking the key to immune protection, and that’s been very hard to do,” said Dr. John Bartlett, chief of the division of infectious diseases at Johns Hopkins School of Medicine.

Vaccine research has caused quite a bit of frustration among AIDS researchers, Bartlett said, and many in the AIDS research community are not enthusiastic about treating those who are uninfected unless there is a specific high-risk patient population for whom it makes sense.

“There are people waiting in endless lines because they have HIV, so I don’t see how we can use those resources for people who don’t even have HIV, especially when the disease can be very well-prevented with condoms,” said Bartlett.   “Right now the three big focuses are prevention, cure and immune activation,” he said.

Several studies have been key in moving HIV treatment forward, including a large 2009 study based in Thailand, where AIDS experts tested the first HIV vaccine, which reduced the risk of infection by more than 30 percent.

In a study published in the summer of 2010, experts expressed optimism for a vaginal gel, intended to be used by women during sex. Clinical trials showed that the gel reduced the risk of a woman acquiring the HIV infection by 39 percent.

Despite the numerous rays of hope, experts warn that, while research has contributed to positive steps in understanding the disease, findings are preliminary and a cure is far away.

“This [vaccine] is about a vibrant immune response,” said Dr. Myron Cohen, chief of the division of infectious diseases at University of North Carolina, Chapel Hill. “But that is really not the same as demonstrating prevention or control of HIV.”