Billions of vaccine doses are wasted every year — not because of manufacturing failures or supply shortfalls, but because of broken cold chains. A temperature spike in a warehouse, an unreliable refrigerator in a rural clinic, an aircraft cargo hold too cold: the "cold chain" that keeps vaccines viable from factory to arm is fragile, expensive, and imperfect.
Now, a team of UK researchers has developed a potential solution inspired by one of nature's most resilient survivors: the resurrection fern.
The resurrection fern (Pleopeltis polypodioides) grows on trees in dry climates across Africa and the Americas. During droughts, it appears to die completely — shriveling into a brown husk — only to spring back to vivid green life within hours of rainfall. Its survival secret is a sugar called trehalose, which stabilizes the plant's cells during extreme dehydration by creating a glassy protective layer around cellular structures.
Researchers at the UK's National Institute for Health and Care Research (NIHR) borrowed that trick directly. Working with vaccine developer Stablepharma, they used trehalose to convert a standard tetanus-diphtheria vaccine from a liquid into a stable powder.
The results were striking. In laboratory tests, the powder remained viable for a full year at room temperature — and survived cycles of extreme temperature swings, from -4°F to 104°F (the kind of thermal stress a vaccine might experience moving from a cold cargo hold to the back of a truck on a hot rural road in sub-Saharan Africa). Where a conventional liquid vaccine would have been rendered useless, the powder held.
A Phase I clinical trial enrolled 60 participants to test the powder's safety and immunogenicity — whether it produces an adequate immune response. The results confirmed it was safe and well-tolerated, with immune responses comparable to the conventional temperature-controlled version of the same vaccine.
"This obviously has potential to remove cold chain dependence, reduce wastage and improve access," said Professor Saul Faust, director of the NIHR Clinical Research Facility at Southampton.
The implications for global health are substantial. In high-income countries, cold chain failures are costly inconveniences. In low and middle-income countries — particularly in rural Africa and parts of Asia — they can be catastrophic. A vaccine that survives room-temperature storage for a year requires far simpler infrastructure to deploy. It could be distributed by community health workers without refrigeration, stored in basic facilities, and remain effective even when power supplies are unreliable.
A larger trial involving 160 participants is now in planning. Because the tetanus-diphtheria vaccine involved is already approved for human use, the path to commercialization is shorter than for an entirely novel product — only the delivery method is new.
The trehalose technology isn't limited to this vaccine alone. Stablepharma believes the same approach could work for other traditionally formulated vaccines, as well as some medicines — including monoclonal antibodies — that currently require refrigeration throughout their lifecycle. Newer mRNA vaccines would not be candidates for this powdering method due to their more complex molecular structure.
The resurrection fern spent millions of years perfecting a solution to the problem of desiccation. It may have just handed scientists the key to one of global health's most persistent logistical challenges.
