Many vaccines need to be kept continuously at cold temperatures, referred to as a “cold chain.” Without it, they may lose their efficiency. But, keeping a vaccine refrigerated poses a challenge, especially in remote and impoverished regions of the world. Now, a stable and affordable way to store viral vaccines for weeks at a time at temperatures up to 40ºC has been developed.
The new method combines the active ingredients in existing vaccines with a sugary gel, where they remain viable for eight weeks or more, even at elevated temperatures. The work is published in Scientific Reports in a paper titled, “Thermal Stabilization of Viral Vaccines in Low-Cost Sugar Films.”
The development of thermally stable vaccines can increase vaccine accessibility worldwide. In the paper, the researchers from McMaster University detail a simple and cost-effective method for stabilizing live vaccines that uses FDA-approved materials.
“This, to us, is the ultimate application of this technology,” said the paper’s lead author Vincent Leung, PhD, an assistant professor of chemical engineering at McMaster University. “To imagine that something we worked on in the lab could one day be used to save people’s lives is very exciting.”
Combining the vaccines and the sugars—pullulan and trehalose—is almost as simple as stirring cream and sugar into coffee, the researchers say. Trehalose is a disaccharide that is commonly used as a cryoprotectant and stabilizing agent. Pullulan is a polysaccharide with good film-forming abilities that is used in the food industry to extend the shelf life of food.
The authors dried enveloped DNA (Herpes Simplex Virus type 2) and RNA (Influenza A virus) viral vaccines in a pullulan and trehalose mixture. The live-attenuated HSV-2 vaccine retained its efficacy for at least two months of storage at 40°C, while the inactivated influenza vaccine was able to retain its immunogenicity for at least three months of storage at 40°C. The authors write that “this work presents a simple approach that allows thermo-sensitive vaccines to be converted into thermo-stable vaccines that do not require refrigeration, thus contributing to the improvement of vaccine deployment throughout the world.”
The new vaccine-storage method suspends the active components of a vaccine in a tiny one-dose container filled with a sugar-gel combination that dries to seal in the vaccine. Later, clinicians reconstitute the vaccine with water and administer it to patients as they ordinarily would.
“Often, complex problems have simple solutions. It just takes the right team,” said Miller. “The best research comes from merging fields, when you do something with someone else that you couldn’t do alone.”
The method creates light, durable, and compact doses that would be ideal for shipping Ebola vaccine, for example, to affected regions of Africa, the researchers said. Maintaining the cold chain is a significant barrier to inoculating people in remote or poor regions of the world, where the infrastructure to refrigerate and transport vaccines smoothly may not be available. The cold-chain challenge is so great, the researchers say, that in some regions, vaccines must be transported by camels bearing solar-powered mini-refrigerators. There are some populations that never receive vaccines.
The process adds only marginal cost to preparing a vaccine and eliminates almost all the cost of transporting it—which can account for 80% of the total cost of inoculation.”You can spend all kinds of money developing a vaccine, but if it is deactivated by high temperature an hour before you can give it to someone, it doesn’t matter,” said co-author Ali Ashkar, PhD, DVM, a professor of pathology and molecular medicine specializing in immunology.
“If you can’t get vaccines to the places where people need them, there’s no point in having them,” added co-author Matthew Miller, PhD, an assistant professor in the department of biochemistry and biomedical sciences whose laboratory specializes viral pathogens.
The materials in the storage medium are already approved by the FDA, simplifying the path to commercialization. “All the pieces are ready to go,” said co-author Carlos Filipe, PhD, chair of chemical engineering at McMaster. “It’s actually quite simple compared to the technology required to create a vaccine itself.”
The researchers are working with a commercial partner to get the technology to market.