PATH Scientists Discover Cheap, Easy Way to Protect Vaccines from Hot and Cold
Scientists at PATH, the Seattle-based nonprofit that works to improve health in poor countries, have found a cheap and simple way to tackle one of the vexing challenges of global health: how to keep vaccines from going bad when they get either too hot or too cold.
PATH scientists, with help from collaborators at U.K-based Arecor and University of Colorado, said they were able to develop a new formulation of hepatitis B vaccine that was able to withstand temperatures as high as 37 degrees Celsius (98.6 degrees Fahrenheit) for a year’s worth of shelf life, while also remaining stable at temperatures as cold as -20 degrees Celsius (-4 degrees Fahrenheit). The new formulation was well-tolerated in animals. The findings were published recently in the scientific journal Vaccine.
Public health officials have been searching for decades for practical methods to deliver vaccines into remote places of the African bush, where there’s no consistent source of electricity, or enough space in refrigerators. Current vaccines, except for the oral polio vaccine, must be shipped and stored in a “cold chain” that preserves them at temperatures between 2 and 8 degrees Celsius (35.6 degrees to 46.4 degrees Fahrenheit), according to the World Health Organization. Any method that allows major vaccines to be stored for a year at room temperatures, instead of in refrigerators, could make it much easier to store vaccines in hot, remote places, where millions of people live around the world.
Along with improved sanitation, mass vaccination is one of the key forces credited with raising life expectancies from about 47 in 1900 to about 77 at the turn of the millennium in wealthy countries. Vaccine technology has been improving in recent years, and raising its profile in the pharmaceutical industry. The market is estimated to grow from an estimated $10 billion in 2007 to some $24 billion globally by 2012, according to a research report from Kalorama Information.
“This could be very far-reaching. We hope this will impact the status quo in the future,” says Dexiang Chen, a senior technical officer for vaccine stabilization at PATH.
How did the researchers do it? After years of testing, the scientists found two 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.