Science News Archive

Sugar sarcophagus keeps viral vaccines viable

Scientists have produced a sugar sarcophagus to keep viral vaccines viable without refrigeration.

One of the leading reasons why many preventable diseases are so prevalent in the third world, despite the benefits and relatively low costs offered by vaccination, is the necessity to keep many vaccines cold. In fact, this "cold chain" as it's known, can contribute up to 14% of the overall cost of the vaccine.

But if they're not kept cold, many viral vaccines, especially live ones like polio, quickly become inactivated, rendering them useless. And in countries where electricity supplies are often absent or intermittent, populations are highly dispersed and communications are poor, delivering vaccines in a viable state to the people who need them is almost impossible.

Now scientists in the UK have found a way to produce a glassy sugar-based casket that can keep viral particles in pristine condition for over 6 months without any need for refrigeration.

Writing in Science Translational Medicine, Robert Alcock from Cambridge Biostability Ltd, together with colleagues based in Oxford, show how two sugars - sucrose (what goes in your tea) and another disaccharide, trehalose - can form a dry glassy solid that, when it dries, can encase and protect viral particles, preserving their integrity.

The team tested two viruses, vaccinia, a member of the poxvirus family used to protect people against smallpox and also to deliver antigens from other infectious diseases including TB, and adenovirus 5, a cause of the common cold which is also used as a viral vector to deliver foreign antigens.

When encased within the dried sugar crystals, full activity could be recovered for both viruses up to 6 months later, even when they were kept at 45 degrees. Usually the infectivity of these agents degrades within hours.

This, say the researchers, could make a massive contribution to attempts to improve health in resource-poor countries where diseases like malaria and TB, for which vaccines are now entering trials, are currently killing more than 5 million people per year.

21st Feb 2010