A major difficulty with large vaccination campaigns is storage and transport of vaccine material. Most vaccines must be stored at low temperatures and require refrigeration, which isn’t always available in remote villages or over long distances of travel.
A key element of the successful campaign to eradicate smallpox was the availability of a freeze-dried vaccine. The vaccine could remain stable at relatively high temperatures, long enough to be administered in remote areas. Unfortunately, similar vaccines are not currently available for all diseases. Many vaccines still require refrigeration and have a relatively short shelf-life, and the countries that are typically in need of large-scale vaccination efforts are also the ones lacking a ready infrastructure to support such programs.
Looking to the future of vaccine development, however, researchers at the Jenner Institute of the University of Oxford recently demonstrated that it may be possible to store vaccine materials for long periods of time within sugar-stabilized membranes. Starting with a small filter-like membrane, the researchers coated it with an ultrathin layer of sugar glass, with the viral particles trapped inside it. In this form, the viruses the researchers used in their study could be stored at temperatures of up to 113°F for six months without losing their ability to provoke an immune response. By comparison, when maintained in liquid storage at 113°F for just one week, one of the two viruses tested was essentially destroyed.
The researchers caution that although their results were promising, additional testing is needed to determine whether trapped viruses can remain stable over periods of time when the surrounding temperature varies. During shipment, they state in their paper, vaccine material could encounter unpredictable temperature fluctuations, including “both heating and accidental freezing in, for example, the hold of an aircraft or the [trunk] of a car.” Any viable storage technique for vaccine material would have to remain effective in such situations.
The viruses tested are also not the ones used in any vaccine currently on the market. They are, however, promising possibilities to be used in vaccines for malaria and HIV, and new vaccines for tuberculosis. As the researchers point out in their paper, those three diseases kill a combined five million people each year, and are major problems in countries that lack the refrigeration and transport capabilities to maintain cold storage and distribution of vaccines. At this point, even if vaccines could be developed against malaria and HIV today, many people in remote areas would be unable to benefit from them without massive efforts and extremely expensive transport and distribution programs. Similarly, while there is an existing vaccine for tuberculosis, it has strict refrigeration requirements that make storage and transport problematic. With this stabilization method, however, widespread vaccination campaigns may be possible in areas previously difficult or impossible to reach.
“Long-Term Thermostabilization of Live Poxviral and Adenoviral Vaccine Vectors at Supraphysiological Temperatures in Carbohydrate Glass,” by R. Alcock; S.D. De Costa; M. Hanlon at Cambridge Biostability Ltd. In Cambridge, UK; M.G. Cottingham; C.S. Rollier; J. Furze; A.J. Spencer; J.D. Honeycutt; D.H. Wyllie; S.C. Gilbert; M. Bregu; A.V.S. Hill at University of Oxford in Oxford, UK; S.D. De Costa at Nova Bio-Pharma Technologies Ltd. In Leicester, UK. Published in Science Translational Medicine, 17 February 2010.