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Scientists have developed a new technique for preserving and transporting the most commonly used vaccine against tuberculosis, improving delivery in resource-poor settings.

Most developing countries — especially those in Africa, Asia, Latin America and the Pacific region — use the Bacillus Calmette-Guérin (BCG) vaccine to help prevent the spread of TB.

But the traditional freeze-drying technique used to create the vaccine can make it less effective, and it must be refrigerated.

The team led by David Edwards of US-based Harvard University developed a cheaper spray-drying technique, which produces a more effective vaccine that can be stored at room temperature.

The spray-drying process is similar to that used to dry food, to produce powdered milk for example.

Crucial to the technique is removing salts and other compounds from the sample of TB bacteria before it is dried. These are normally required for storing and freezing vaccines, but can damage the bacteria when the sample is evaporated. 

Jerome Amir Singh of the Nelson R. Mandela School of Medicine, South Africa, told SciDev.Net that the death toll due to TB is highest in environments with high HIV prevalence, which typically lack electrification, cold storage facilities and transport infrastructure.

"The development of a dry spray TB vaccine will help negate some of these factors. Most importantly, it will significantly boost the efficacy of the BCG vaccine, thereby providing the world with a potent and vastly improved weapon in the war against TB," he said.

Tuberculosis kills about two million people a year. About two billion people — one-third of the world's population — carry the bacterium, but it is active only in around ten per cent of these people.

The study was published online last week (13 February) in Proceedings of the National Academy of Sciences.

Link to abstract in Proceedings of the National Academy of Sciences

Reference: Proceedings of the National Academy of Sciences doi 10.1073/pnas.0611430104 (2007)

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