The most promising vaccine to replace the world's 91-year-old tuberculosis jab does not protect against the disease, according to results released on February 04 of large-scale trials conducted among infants in South Africa.
Doctors have had high hopes for the formula, known as MVA85A, as the existing Bacille-Calmette-Guerin (BCG) vaccine does not protect against pulmonary TB, the most common form of the disease among adults and adolescents.
MVA85A was found to be safe and had no side effects, but "did not provide statistically significant protection" against the TB microbe, the researchers announced.
The trial was a so-called Phase IIb, comprising the intermediate step between the second and final phases of the long process by which drugs are vetted for safety and efficacy. It is the first TB vaccine candidate to reach this stage since BCG, which was licensed for humans in 1921.
The trial, launched in 2009, saw the drug tested on 2,800 infants in South Africa's Western Cape province who did not have TB or the AIDS virus. All of the children were given BCG at birth. Half of them also received a single dose of MVA85A at four to six months of age, and the others were given a harmless placebo.
They were then monitored over 37 months. Among the BCG-plus-placebo group, there were 39 cases of TB; among the BCG-plus-MVA85A group, there were 32. The difference amounts to vaccine efficacy of 17.3 percent. The results, published in the journal The Lancet, are disappointing but should also provide vital insights, said senior researcher Helen McShane of the University of Oxford.
"The results from this study should let us know far more about the type and level of immune response required, and that will boost future efforts to develop an effective TB vaccine," she said in a press release.
"The difficulty of this task is one reason why there has not been a new TB vaccine since BCG was developed more than 90 years ago, but one is still urgently needed and I'm not about to give up now," she added.
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