By Jane Dreaper
Health correspondent, BBC News
Vaccines must be kept refrigerated at the moment
Scientists at Oxford University have found a way of keeping vaccines stable without refrigeration.
Writing in Science Translational Medicine, they say the breakthrough could significantly help efforts to immunise more children in rural Africa.
The researchers mixed the vaccines with two types of sugar before slowly drying them on a filter paper.
This preserved the jabs, which were then easily reactivated when needed for injection.
The need to keep vaccines cool - to stop them deteriorating - is often difficult in developing countries where fridges, clinics and an electricity supply cannot be taken for granted.
Writing in the journal Science Translational Medicine, the scientists describe how they managed to keep vaccines stable for up to six months at 45C.
They used sucrose and another sugar called trehalose, which is known for its preservative properties.
'Simple and cheap'
The research was funded by the foundation set up by Bill and Melinda Gates. It involved a collaboration between the university scientists and a company, Nova Bio-Pharma Technologies.
The lead investigator, Professor Adrian Hill, said: "If we could convert all the standard vaccines to a solution like this, it would mean they're cheaper to deliver, because they'd survive at room temperature - and so there'd be scope to vaccinate more children.
"The technology is simple and extremely cheap - and there are no more scientific hurdles to overcome.
"Our tests were pretty tough as we used live viruses. So we feel that having stabilised those more fragile vaccines, this method should work for other vaccines containing dead protein.
"It's now just a matter of developing the technique, trying it out in Africa and seeing if it can be made on an industrial basis. This could happen within five years."
Another member of the research team, Dr Matt Cottingham, said: "Without the need for refrigeration, you could even picture someone with a backpack taking vaccine doses on a bike into remote villages."
The GAVI Alliance, a public-private partnership working to accelerate immunisation in 72 of the world's poorest countries, welcomed the news.
"Keeping vaccines at the correct temperature all the way from the factory to children in the poorest and most remote communities is always an enormous challenge so new ideas to remove barriers to the life-saving benefits of immunisation are extremely welcome," said the alliance's communication director, Dan Thomas.