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[PARIS] A new candidate vaccine can significantly reduce rates of tuberculosis (TB) infection in HIV-positive individuals, according to researchers.

The results of the seven-year Phase III 'DarDar' trial in Dar-es-Salaam, Tanzania, were presented at the 39th Union World Conference on Lung Health in Paris, France, this week (20 October). This is the first successful demonstration of any protective effect against TB in HIV/AIDS patients.

TB is the leading cause of death in people with HIV/AIDS, accounting for around 40 per cent of overall mortality. HIV/AIDS patients are at particular risk from multidrug or extensively drug-resistant TB, particularly where drug resistance testing is unavailable.

The standard vaccination against tuberculosis is the BCG. However, as BCG consists of live Mycobacterium, there is a risk that HIV patients can contract TB from the vaccine due to their weakened immune systems. The new M. vaccae vaccine consists of dead bacteria, and previous Phase II trials have confirmed its safety in HIV/AIDS patients.

The 2,000 subjects in the DarDar trial were HIV-positive and had received a standard BCG vaccination. They showed no signs of TB infection and had healthy immune systems. Following the BCG, half of the group were given five doses of the new vaccine while the other half was given a placebo vaccine.

The trial showed a significant reduction in TB infection — 52 cases were observed in the placebo group, while just 33 were observed in the vaccinated subjects — over an average follow-up period of 3.5 years.

"Our research group was focused on developing an improved TB vaccine specifically for [HIV/AIDS patients]. We are delighted that the vaccine was shown to be effective," Ford von Reyn, professor of medicine at the US-based Dartmouth Medical School and leader of the study, told the press.

"It is exciting to think we may be able to offer a protective TB vaccine to people after they test HIV-positive."

"This study demonstrates that collaboration between industrialised and developing countries in addressing an international problem can be done successfully," adds co-researcher, Kisali Pallangyo of Muhimbili University in Tanzania.

Von Reyn says that an M. vaccae-based vaccine would be cheap to produce and could be in use within three years. "We hope that further research will develop a vaccine conferring even greater protection," he concluded.