Fridge-free tetanus vaccine well tolerated in first human trial

A vaccine dose can spend months in transit, moving from refrigerated trucks to national cold rooms, district cold rooms, health facility fridges and finally cold boxes carried to outreach sessions. One broken link can leave it unusable. In the U.K., the biotechnology company Stablepharma began a first human trial in April 2025 of a tetanus-diphtheria vaccine designed to stay stable without a fridge.

Vaccines generally must remain between 2°C and 8°C, and some need much colder conditions. This uninterrupted refrigeration is called the cold chain, and it depends on reliable electricity, refrigerators, fuel, maintenance technicians and trained health workers. In remote areas, areas affected by conflict and facilities with unreliable electricity, each of these demands becomes harder to meet. Immunization programs have built workarounds, such as the vaccine vial monitor, a heat-sensitive label that signals whether a vial can still be used, and the controlled temperature chain, which allows specific approved vaccines to stay outside the standard range for a limited, monitored period before administration.

The new candidate, known as SPVX02, relies on trehalose, a sugar that protects some plants and organisms during drying. The vaccine is freeze-dried with trehalose into a powder, stored without refrigeration and mixed with water before injection. In the trial, sixty healthy adults in the U.K. were randomly assigned to receive either this version or one of two licensed tetanus-diphtheria vaccines. The experimental formulation was well tolerated and produced excellent immune responses. Laboratory stability data show it can remain stable for at least 24 months at temperatures of up to 30°C.

If later evidence and regulatory reviews are favorable, the experts see several gains. In the Sahel and the Horn of Africa, mobile teams could reach pastoralist and nomadic communities without depending on ice-pack production. In island, mountainous and sparsely populated settings, vaccines could tolerate longer journeys, and in humanitarian emergencies they could be positioned closer to displaced people even where electricity and secure transport are intermittent. Lower needs for fuel, equipment and specialized transport could also reduce costs and the environmental footprint of vaccine delivery. No timeline is given for any of this, and each product would need its own evidence and approval.

The approach is not a silver bullet. The product is not ready for African immunization programs, and larger, more diverse studies are still required. Africa already has precedents: MenAfriVac, the meningitis A vaccine developed for Africa, was authorized for use at temperatures up to 40°C for four days immediately before administration, and its use in Benin showed that vaccinators could reach remote populations with a lighter logistical burden. The experts also stress that fridge-free does not mean logistics-free.