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Study finds TB vaccine booster safe for humans, but effectiveness is unproven

Tuberculosis is relatively scarce in Canada and other developed Western countries, but is estimated by the World Health Organization to infect as many as nine million people worldwide and kill upward of one million each year. Only babies born in Nunavut are vaccinated, because of the high rate of tuberculosis there.

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A drug intended to boost the immunity provided by the tuberculosis vaccine is being tested at McMaster University and has been found safe for use in humans, but not yet proven effective, according to a new study.

While the booster is many years and clinical trials away from being approved for mass production, the finding offers some hope for the global fight against tuberculosis and follows news in recent weeks that a New Brunswick university student and a person at an Ontario high school were infected with the virus.

"There's the potential to dramatically change the course of TB," said the lead author of the study, Fiona Smaill, chair of pathology and molecular medicine at the Michael G. DeGroote School of Medicine at McMaster in Hamilton.

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Tuberculosis is relatively rare in Canada and other developed Western countries, but is estimated by the World Health Organization to infect as many as nine million people worldwide and kill upward of one million each year. No one in Canada is vaccinated any more except babies born in Nunavut, which has a high rate of tuberculosis.

The current vaccine, known as Bacille Calmette-Guérin, or BCG, is routinely given to infants in countries with high rates of tuberculosis and shields them well. But its efficacy wanes over time.

Scientists have spent decades searching for a more effective vaccine or a booster to enhance the protective qualities of BCG.

The McMaster study was a first-phase clinical trial, which examined whether the drug could be tolerated by humans and could engage the immune system. The trial began in 2009 with 24 healthy people, half of whom had been vaccinated with BCG.

The booster's effectiveness will be determined in additional clinical trials that Dr. Smaill anticipated would take place over the next eight or more years.

Still, the booster – known as AdHu5Ag85A and based on a genetically modified cold virus – has been shown to work in mice, guinea pigs and goats, according to the study, which was published online on Wednesday in the journal Science Translational Medicine.

Dr. Smaill said her team has approached Aeras, a biotechnology not-for-profit corporation that invests in TB vaccine advancement, for funds to continue research. A spokesperson for Aeras was unable to comment immediately.

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A dozen TB vaccines or boosters are now in clinical trials around the world, according to the World Health Organization.

For years, the most promising was one developed by researchers at Oxford University in Britain. But a clinical trial involving nearly 3,000 healthy babies in South Africa determined the vaccine was no more effective than BCG, which has been in use since 1921.

On Tuesday, officials from health advocacy groups including the World Health Organization, UNICEF, and the U.S. Centers for Disease Control and Prevention announced a strategy to eradicate tuberculosis in children. They estimated implementing it would cost $120-million per year and are searching for funding.

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