British researchers have developed a new way of preserving vaccines without refrigeration by sealing the vaccine's live viruses inside glass made of sugar.
The vaccines trapped in the sugar-glass could be stored at 45 C for four months without any degradation, and suffered only a small amount of degradation after a year of storage at 37 C, the researchers say.
Their study, published this week in the journal Science Translational Medicine, is a proof-of-concept of the technology. The researchers said further testing is needed to see if the sugar-glass can withstand temperature extremes and physical conditions typically seen in overseas shipping.
The technique involves mixing the vaccine's live viruses with two sugars, sucrose and trehalose. The solution is then dried out on a plastic film and hardens into glass.
Inside the sugar-glass, the vaccine is immobilized and kept in suspended animation.
To prepare the vaccine for injection, the glass is flushed with water and quickly dissolves, reactivating the vaccine. The new technology, developed by manufacturer Nova Bio-Pharma Technologies, could improve the distribution of vaccines to tropical countries that may lack the infrastructure necessary to keep vaccines stable .
"Currently, vaccines need to be stored in a fridge or freezer," said the study's lead author Matt Cottingham of Oxford University. "That means you need a clinic with a nurse, a fridge and an electricity supply, and refrigeration [trucks] for distribution.
"If you could ship vaccines at normal temperatures, you would greatly reduce cost and hugely improve access to vaccines," he said, in a statement.
A study of the technology, using two malaria vaccines that are currently in human clinical trials, found that the vaccines could be used even after up to a year in storage at tropical temperatures.
Sugars like the ones used in the study are currently used to preserved biological molecules, and the researchers say that those preservation properties are at work in the glass.
Currently, Nova's technology, called the Hypodermic Rehydration Injection System, is in the form of a plastic cartridge that screws into standard vaccine syringes, but the researchers say that the sugar-glass could be adapted to be put inside the syringes themselves.