High hopes as new TB vaccine proves effective

Hope of an effective tuberculosis (TB) vaccine has been boosted by findings from the Tanzanian trial of a new TB vaccine showing that TB infection in HIV-positive patients was reduced by 39 percent.



The TB vaccine "mycobacterium vaccae" was tested in a double-blind, randomised, controlled trial that ran for seven years and involved 2,013 HIV-positive Tanzanians, and was a collaborative effort between scientists from the Dartmouth Medical School in the US, and Tanzania's Muhimbili University of Health and Allied Sciences.



"This is the first TB vaccine to show effectiveness in any clinical trial," Dartmouth's Dr Richard Waddell told IRIN/PlusNews. "It will re-energize the search for an even more effective TB vaccine, which is especially urgent in Africa."



According to the UN World Health Organization (WHO), TB is the leading cause of death among people living with HIV in Africa; globally, one in four TB deaths is HIV-related.



Trial participants were given five doses of the vaccine over a year, after which they were monitored every three months for 3.3 years, but the study was terminated early because of "significant protection against definite tuberculosis". Among those who received the vaccine, 33 were infected with TB, compared with 52 of those who got a placebo.



BCG booster



"We found the vaccine to be a booster for BCG [Bacille Calmette Guerin, the TB vaccine given almost universally to infants in sub-Saharan Africa] which wears off with time," Waddell said. "All the study participants had been vaccinated with BCG in childhood."



WHO has revised its guidelines on the use of BCG to reflect the risk of TB infection from the vaccine, a weakened form of the disease, in HIV-infected infants.



A heat-killed version of a bacterium similar to TB is used in the mycobacterium vaccae vaccine, so there is no risk of infection through vaccination, even in patients with compromised immunity.

A vaccine would cut the chain of transmission of the epidemic, and would have a massive impact on the HIV and TB epidemic in Africa

Raddell said the investigators were working with a US pharmaceutical company to develop a form of the vaccine that could be mass produced. "If all the legal work and efficacy tests go smoothly, the drug could be available within two years." The drug would be "inexpensive" to produce and would therefore be able to be used widely.



More research needed



The importance of finding an effective TB vaccine cannot be overestimated. "A vaccine would cut the chain of transmission of the epidemic, and would have a massive impact on the HIV and TB epidemic in Africa," said Dr Marcos Espinal, executive secretary of the Stop TB Partnership, a global initiative that works closely with WHO.



He said at least 10 experimental TB vaccines were in clinical trials at the moment, so hope was high that at least one of them would succeed and be in production by 2015.



"There is plenty of good research going on but much more needs to be done," Espinal said. "Funding for research for vaccines is still not at the levels we need it to be."



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