TB vaccine trial: “A stepping stone on a very long journey”

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In the wake of announcing clinical trial results that showed  a candidate for a tuberculosis vaccine was safe, but did not protect babies from infection and disease, researchers are emphasizing what they have learned, and how it might yet pave the way for a long-term answer to the epidemic.

The trial of MVA85A, a candidate intended to boost the effectiveness of the current vaccine against tuberculosis widely used on infants, took place over three years and enrolled more than 2700 children in a rural area near Cape Town South Africa. Divided randomly into groups that received a placebo and received the vaccine, the children all had received the currently available Bacille Calmette-Guerin — BCG — vaccine at birth.The BCG vaccine offers limited protection from the spread of tuberculosis from lungs to other parts of the body, but does not protect against pulmonary infection, the source of most tuberculosis transmission, and does not prevent reactivation of pulmonary infection.  By the end of the study, 32 cases of tuberculosis disease were found  among the infants who received the MVA85A vaccine and 39 cases of the disease were found among children who had received the placebo.

While the results showed the vaccine candidate would not provide the benefits researchers were seeking, the completion of a clinical trial of that scale and length in a setting where continuity  by participants can be challenging, with clear results, is in itself a success, researchers emphasized in a conference call today.

The positive news from the trial, which established the safety of the vaccine, will simplify and reduce the risk of failure of future trials that use the same vector used in MVA85A, researchers said.

In addition, samples collected in the course of the trial from the 71 children who did get tuberculosis disease will be a source for further analysis that can yield information on specific disease risk indicators, information that a representative of one of the organizations collaborating on the research called “invaluable.”

With that information, Tom Evans, interim Chief Executive Officer of Aeras, a nonprofit biotech organization that provided funding for the trial, future trials can identify those at highest risk for tuberculosis, and enroll fewer people.

That is important, because more trials will be needed to reach what University of Oxford researcher, Helen McShane, who developed the vaccine candidate, called “the long-term answer” to tuberculosis. McShane stressed that while new medicines that are effective in treating drug-resistant tuberculosis, and treating the disease in children and people living with HIV, as well as diagnostic tools that can deliver reliable results at points of care in endemic areas, are needed immediately, a vaccine that offers protection from tuberculosis will have the greatest impact on the epidemic eventually.

Tuberculosis is estimated to kill 4,000 people worldwide every day, while continuing to spread in increasingly drug-resistant forms.

“We have to just keep going,” McShane said, who called the trial “a stepping stone on a very long journey, but one that must be taken.”





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