February 04, 2013
South African TB Vaccine Trial Fails, More Coming
A long-awaited study of the first new tuberculosis vaccine in nearly a century shows that it offers no significant advantage over the existing vaccine in protecting babies from TB infections. The results, based on a study of about 3,000 babies in South Africa, were disappointing but not a complete surprise.
The vaccine, called MVA85A, is the most advanced of more than a dozen TB vaccines now in human clinical trials. Scientists are still trying to assess why the trial failed and how these results can guide future studies.
The only current TB vaccine -- known as Bacille Calmette-GuDerin, or BCG -- was developed in 1921. It is still used to immunize babies in countries with high rates of TB. But BCG's protection lasts only a few years, and provides no immunity against the most common TB bacterium that attacks the lungs of teens and adults, and which is spread easily through coughing and sneezing.
TB kills 1.4 million people around the world each year. More than 9 million new TB cases are diagnosed every year.
The routine treatment for TB is a 6-to-9-month course of powerful antibiotics -- a regimen that can be costly and difficult to maintain, especially in poor and remote regions of the world.
The study was published in the British medical journal The Lancet. Researchers tested the MVA85A vaccine in some 3,000 healthy South African babies who had already been given the BCG vaccine. Half of the babies got the new vaccine; the other half did not, serving as a placebo or control group. Over the next two years, 32 babies in the MVA85A group came down with TB, compared with 39 in the placebo group. The modest advantage enjoyed by the vaccine group is not statistically significant, according to the researchers.
While the findings are disappointing, the scientists believe their study is a medical milestone. A University of Oxford researcher who helped develop the vaccine, Helen McShane, said ``This is the first efficacy trial of a new TB vaccine since Bacille Calmette-GuDerin, a significant step in itself, and there is much that we and others can learn from the study and the data it produced.'' Medical experts commenting on the trial say it produced important new evidence about human immunity against TB.
MVA85A was developed with support from an international consortium of public and private groups, including Aeras, a non-profit U.S. biotech firm funded in large part by the Bill & Melinda Gates Foundation.