Researchers at the University of Bath believe they have solved one of the major challenges for vaccines – keeping them cold enough to be used. Nearly half of all vaccine doses are discarded before use due to exposure to the wrong temperatures.

The team at Bath working on a new tuberculosis (TB) vaccine have developed a technique to prevent crucial vaccine components – the antigen and the vaccine – from spoiling outside of a fridge. This means a thermally stable vaccine that can be reliably delivered to remote areas around the world is more likely.

The technique, called ensilication, “shrink-wraps” vaccine proteins in position using layers of silica that build up into a cage around the molecules. This means the proteins don’t unravel when exposed to temperatures that would usually break them down. The proteins are held in place until ready to be removed from the silica cage and delivered.

“To make the vaccine as effective as possible it needs to be thermally-stable, or in other words not spoil outside of a fridge, which is why we’re really encouraged by these results. Cold-chain storage leads to a lot of wastage and expense which could be avoided by ensilication,” said researcher Ayla Wahid.

The research team from the Departments of Biology & Biochemistry and Chemistry first demonstrated that the TB antigen ag85b and a vaccine fused with the adjuvant protein Sbi are sensitive to breaking down outside of refrigerated temperatures. They then showed that these vaccine components were protected from heat damage when ensilicated and kept on a shelf at room temperature for long periods of time without loss of structure and function.

This is first time that ensilication has been used to improve the thermal stability of proteins in a vaccine setting, after proof-of-principle work using model proteins.

 The technique, developed by Dr Asel Sartbaeva, can also be used for many different kinds of vaccines.

“Our results reveal the potential of ensilication in storing and transporting life-saving vaccines at ambient temperatures globally – in particular to remote areas of developing countries where disease rates are often highest,” he said.

“With up to 50% of vaccines being thrown away, and refrigeration raising vaccine costs by up to 80%, this is a major global health challenge that we need to overcome. By demonstrating for the first time that ensilication works to protect vaccine-relevant proteins from breaking down outside a fridge we’re a big step closer to achieving this goal.”

Nick Flaherty