UK-based biotechnology company Stablepharma has reported encouraging results from the world’s first clinical trial of a fridge-free tetanus-diphtheria vaccine, potentially opening a new pathway for improving vaccine access while reducing the environmental burden associated with conventional cold-chain storage and transportation.

The Phase I trial evaluated SPVX02, a reformulated tetanus-diphtheria vaccine developed using Stablepharma’s StablevaX thermostabilisation technology. The study found that the vaccine was well tolerated, with no vaccine-related serious adverse events reported. 

The trial involved 60 healthy adults and was conducted at the NIHR Clinical Research Facility at University Hospital Southampton, through the NIHR Biomedical Research Centre: Southampton, with additional participation from the Medicines Evaluation Unit in Manchester.

Results showed that SPVX02 can be stored at temperatures of up to 30°C for at least two years without compromising its effectiveness. Researchers are continuing to assess whether the formulation can maintain stability for up to four years.

The vaccine also demonstrated resilience under extreme temperature conditions. Researchers found that SPVX02 remained stable and fully potent following three cycles of temperature fluctuations ranging from -20°C to +40°C.

By 28 days after vaccination, all participants who received SPVX02 achieved protective antibody levels against both tetanus and diphtheria. The immune responses were comparable with those generated by currently licensed vaccines.

The findings are particularly significant for global immunisation programmes that depend on uninterrupted refrigeration from vaccine manufacturing facilities through transportation, storage and administration. According to the World Health Organization, around half of vaccines are wasted globally each year, with temperature excursions during storage and transportation contributing to losses.

A vaccine that can remain stable without refrigeration could help reduce these losses and make immunisation programmes more practical in remote and underserved communities where reliable cold-chain infrastructure is difficult to maintain. Reduced dependence on refrigeration could also lower the energy consumption and associated carbon emissions generated by vaccine storage and distribution.

Professor Saul Faust, Director of the NIHR Clinical Research Facility in Southampton and professor of paediatric immunology and infectious diseases at the University of Southampton, who led the study, said the findings suggest that the vaccine could remain safe and effective without refrigeration. He added that larger studies would be needed to confirm whether the technology could transform vaccine storage and delivery globally.

The Phase 1 results follow the launch of a Phase 2b trial, which will evaluate SPVX02 in a larger participant population and provide additional clinical evidence on its safety and efficacy.

Stablepharma CEO and Executive Director, Özgür Tuncer, said, the peer-reviewed findings represent an important milestone for the company’s StablevaX platform and support the potential development of a new generation of thermostable, fridge-free vaccines.

Stablepharma Founder and Board Member, Dr. Bruce Roser, said, reliable fridge-free vaccines could help expand access to life-saving immunisation, particularly in areas where cold-chain infrastructure remains a major challenge.

The technology behind SPVX02 could extend beyond vaccines. Stablepharma’s StablevaX platform is designed to thermostabilise a range of pharmaceutical products, including vaccines, small molecules, peptides and biologics. The company is also working with a partner on the thermostabilisation of small-molecule oncology and anti-infective products.

SPVX02 is a reformulated version of the WHO-prequalified Tetadif tetanus-diphtheria vaccine. Its development has received support from Innovate UK, part of UK Research and Innovation (UKRI), while scientists from the UK Health Security Agency provided specialist laboratory testing.

The programme also highlights the role of UK clinical research infrastructure in helping biotechnology companies translate novel technologies into clinical-stage products. NIHR-funded research infrastructure supported Stablepharma in conducting the first-in-human study and generating the clinical evidence required to advance the technology.

Stablepharma expects to complete the clinical development programme for SPVX02 by 2027. If subsequent trials confirm the Phase 1 findings, the technology could offer a potentially more flexible and sustainable approach to vaccine storage and distribution, particularly in regions where cold-chain limitations restrict access to essential immunisation.