An experimental new vaccine has been successfully tested in humans; one designed to protect against tetanus and diphtheria and that also remains potent after long periods without refrigeration. This gives real hope of overcoming the challenges of vaccinating in areas where maintaining the cold chain has long been a problem. Most vaccines need to be maintained within a strict temperature range from the time they leave the factory to their use in the clinic. Any breaches in this cold chain can spoil the product, wasting vast quantities and exposing people to disease.
For many tropical, isolated or war-torn locations, electricity and frozen containers are out of reach. For years scientists have been exploring potential alternatives. They may have taken a big step forward recently.
This vaccine SPVX02 will be a reformed tetanus-diphtheria booster. Researchers at UK firm Stablepharma have used a natural sugar trehalose to desiccate (turn the liquid into a dry powder) the vaccine, as it is the very same substance that desert plants use to endure periods of extreme dehydration and then revive again. Once dried with this protective sugar, the vaccine can sit at room temperature for long periods.
In a phase 1 trial using 60 healthy adults, the dried vaccine was stored for 1year at 30o C and then mixed with water and injected. The volunteers who received SPVX02 had protective antibody titres against tetanus and diphtheria that were comparable to people who had been given 2 published licensed vaccines. No serious side effects were seen.
Mild-moderate side effects were comparable to those seen with normal tetanus-diphtheria vaccines. Another lab test revealed that the powder could last for an even longer period of time; 2 years at 30 degrees Celsius in a very humid environment and six months at 40 degrees Celsius. Its stability even extended through many freezing to hot cycling rings, such as the transition during shipment.
Definitely, these results are important because, despite the relative low burden, tetanus and diphtheria continue to be life-threatening in resource-limited settings. Both are eminently preventable through vaccination, but continue to be a burden where one’s inability to get a vaccine to a remote community can take a human life. A transportable and storable product that didn t require refrigeration would be a great improvement by reducing both the expense and the waste, allowing immunization to reach those who need it most.
But the technology is not confined to this one vaccine. Stablepharma is in the process of applying this same technology to other crucial vaccines too – hepatitis B and the human papillomavirus. Bigger trials of the tetanus-diphtheria mix are underway to verify the promising results in more patients.
For now, this first effective human study is a modest but significant step forward. It proves that an injectable vaccine does not need a vast and everlasting pipeline of electricity and ice packs to be life-saving. Using a survival skill found in the strongest desert plants, researchers have moved a practical step closer to resilient immunization.
