common stabilizers that could be added to the vaccine. Propylene glycol can be used to keep the Hepatitis B vaccine stable in cold temperatures, while an amino acid called histidine helps to protect the vaccine formulation from excessive heat, Chen says.
Propylene glycol is a common stabilizing solvent found in many pharmaceuticals and consumer products like mouthwash and toothpaste. Histidine is thought to enhance the stability of vaccines that contain adjuvants, or immune-boosting compounds designed to make them more potent, Chen says. These additives are so cheap, they can be combined in a new formulation that only costs an extra one-tenth of a penny, Chen says.
“The important thing is the cost,” he says.
PATH began this project back in 2003, and the vaccine stabilization work has long been supported by the Bill & Melinda Gates Foundation. PATH has started to share this latest finding with vaccine manufacturers and government agencies around the world, in hopes of building up more support for more testing, says Debbie Kristensen, the organization’s group leader of vaccine technologies.
Researchers selected hepatitis B as the model vaccine because it is easy to run tests against, Kristensen says. The vaccine stabilization technology ought to work for other vaccines, too, although scientists will have to run experiments to show it like they did with the hepatitis B vaccine, Chen says.
Plus, more work needs to be done before this reformulated hepatitis B vaccine can really enter the field in a big way. Clinical trials will be required to confirm that the new formulation is both more stable, and also effective at protecting people from infection, Kristensen says.
What has PATH particularly excited is that by reformulating vaccines, it can circumvent many other solutions people have been trying to use for years to preserve vaccines. The list of other techniques includes things like color-coded temperature-monitoring stickers on vials that say whether a vaccine has spoiled, increased amounts of cold-chain equipment, or improved training of healthcare delivery workers. The new alternative is a big advance, Kristensen says.
“This would allow us to prevent the problem from the beginning, by solving it through the vaccine formulation itself,” Kristensen says.
