British researchers have devised a way to capture vaccines in a glass-like membrane composed of sugar, a feat that could eliminate the need for refrigeration of vaccines and revolutionize their distribution in the developing world. Tests have shown that the technique can preserve vaccines for as long as a year at tropical temperatures, according to the report Wednesday in the journal Science Translational Medicine.
Most current vaccines, especially those for children, require refrigeration or freezing for storage. That adds at least $200 million to the cost of distributing vaccines in developed countries and can produce an insurmountable barrier in many developing countries that don't have the infrastructure for such efforts. The need for vaccines that don't require refrigeration has been identified as one of the Grand Challenges in Global Health, a partnership launched by the Bill and Melinda Gates Foundation.
The candy-coated vaccines were developed by a team headed by Dr. Matt Cottingham of Oxford University and are being developed by British specialist manufacturer Nova Bio-Pharma Technologies. The concept is simple: The vaccine is mixed with a solution of the sugars trehalose and sucrose. The mixture is then left to dry out on a simple filter or membrane. As it dries and the water evaporates, the vaccine mixture first turns into a thick syrup, then crystallizes into a stable glass-like membrane. When water is added, the mixture instantly dissolves and is ready to be injected.
Cottingham and his colleagues reported that they studied the technology with two prototype live-virus vaccines they are developing, one based on an adenovirus (the family that includes cold viruses and viruses used in gene therapy) and one on a poxvirus (the family that includes smallpox). They reported that the vaccine was viable after four to six months at 113 degrees Fahrenheit and after a year at 99 degrees F.
"We've developed a very simple way of heat-stabilizing vaccines and shown that it works for two viruses that are being used as the basis for novel vaccines in development," senior author Adrian Hill of Oxford said in a statement. "This is so exciting scientifically because these viruses are fragile. If we are able to stabilize these, other vaccines are likely to be easier."
The new technology, if proved, could greatly simplify vaccine distribution in developing nations. "You could even picture someone with a backpack taking vaccine doses on a bike into remote villages," Cottingham said.
The research was funded by the Gates Foundation and the Wellcome Trust, Britain's largest charity.
-- Thomas H. Maugh II
The immobilized vaccine could be stored in the container on the left. Attaching it to a syringe and pushing water through it would reactivate it for injection. Credit: Nova Bio-Pharma Technologies