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Most Advanced Tuberculosis Vaccine in 90 Years Fails to Boost Protection

Update Date: Feb 04, 2013 11:12 AM EST
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Results from a highly anticipated clinical trial of the most advanced tuberculosis vaccine in 90 years showed that it failed to protect babies against the infectious disease, researchers said on Monday.

The experimental vaccine, known as MVA85A, seemed to have "no significant efficacy" against either TB or infection with Mycobacterium tuberculosis, according to the study published Monday in The Lancet.

The TB research community had hoped that the MVA85A vaccine could be used as a booster to the Bacille Calmette-Guerin (BCG) vaccine, the only existing tuberculosis vaccine, which was created 90 years ago and  is routinely used against the airborne disease that kills around 1.4 million people around the world each year. Researchers wrote that while the new vaccine appeared to be safe, the study found no evidence that it prevented tuberculosis.

The major clinical trial involved 2,797 healthy babies in South Africa between the ages of four and six months of age. The randomized phase 2 trial was designed to further evaluate the safety, immune response, and efficacy of MVA85A in preventing tuberculosis disease in children.

The results showed that babies given the experimental MVA85A vaccine in addition to the standard BCG vaccine were no more protected against the TB bacterium or less likely to develop the disease after three years compared to those who only got the BCG vaccine, researchers Helen McShane of Oxford University in the UK and Hassan Mahomed of Stellenbosch University in South Africa wrote in the study.

Researchers had given the new MVA85A vaccine to 1,399 infants and placebos to another 1,398 babies.  They found that 39 of the infants in the placebo group and 32 of those given the new vaccine had developed TB, and 171 babies in the placebo group later became infected with M. tuberculosis, versus 178 of those vaccinated.

"Despite reaffirming the promising safety profile, the vaccine candidate MVA85A did not offer extra protection against TB in South African infants who had already received the BCG vaccine," McShane said, according to onmedica.com.

Past clinical trials of the vaccine in adults showed promising results and researchers said that the latest trials provided data that could be useful for future studies.

"The vaccine induced modest immune responses against TB in the infants, but these were much lower than those previously seen in adults, and were insufficient to protect against the disease. This is the first efficacy trial of a new TB vaccine since Bacille Calmette-Guérin (BCG), a significant step in itself, and there is much that we and others can learn from the study and the data it has produced," McShane said in a statement.

According to the World health Organization, tuberculosis is the second deadliest infectious disease behind AIDS. Tuberculosis sickened around 8.7 million people and claimed 1.4 million lives in 2011, according to the latest WHO statistics.

The disease is caused by a bacterium that has infected a third of the world's population.  While the bacterium lies dormant in most people, it activates in about 10 percent of people it infects. The activated bacterium then sickens its host and is transmitted to others though coughing and sneezing.  According to WHO, both the active and latent forms of TB can be cured with antibiotics, but it notes that there is evidence that TB is becoming increasingly resistant to standard drugs. 

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