An experimental vaccine helps prevent tuberculosis in people infected with HIV, researchers have found.

The Mycobacterium vaccae, or MV vaccine, reduced the rate of tuberculosis by 39 per cent among 2,000 people infected with HIV in Tanzania, researchers said in Friday's online issue of the journal AIDS.

Tuberculosis accounts for up to a third of AIDS deaths worldwide, and TB worsens HIV, according to the World Health Organization.

"Development of a new vaccine against tuberculosis is a major international health priority, especially for patients with HIV infection," said the study's lead investigator, Dr. Charles Ford von Reyn of Dartmouth Medical School in Hanover, N.H.

The vaccine includes an inactivated form of the bacteria.

It was tested in 2,013 HIV outpatients in Dar es Salaam, Tanzania, who were vaccinated with the traditional TB vaccine (called Bacillus Calmette-Guérin, or BCG) shot as children. Participants were followed every three months for an average of 3.3 years.

In the seven-year, randomized, placebo-controlled trial study, 33 were infected with TB among those who received the experimental vaccine, compared with 52 given a placebo.

The immunization was well tolerated with no increase in the rate of serious adverse events, and there was no harmful effect on HIV viral loads, the researchers said.

The study is the first to show that any type of vaccine can prevent an infectious complication of HIV in adults, Von Reyn said.

Next, researchers need to improve manufacturing methods to produce larger amounts for further studies, and potentially for clinical use, if it is approved by regulators.

The study was sponsored by the U.S. National Institutes of Health.