Fridge‑free vaccines could reach more people, but there are still practical challenges in African settings

Refrigeration plays a critical role in maintaining the efficacy and safety of vaccines and medicines, but its absence poses significant challenges for vaccine delivery in Africa. The University of Kent biotech firm Stablepharma has initiated the first human trial of a tetanus-diphtheria vaccine, which is designed to remain stable without refrigeration. This development has rekindled interest in technologies capable of reducing reliance on refrigeration, particularly in regions with limited infrastructure.

Vaccines often traverse extensive logistics networks from manufacturers to final recipients, involving various storage conditions and temperature-sensitive handling. The cold chain, responsible for maintaining vaccines within their required temperature range—typically between 2°C and 8°C—requires uninterrupted refrigeration, refrigerators, freezers, temperature monitoring devices, and a well-trained workforce. Any disruption along this chain can compromise vaccine potency or even its safety.

Transporting vaccines in remote areas, conflict zones, or facilities with unreliable electricity further complicates the process. In Sudan, for instance, fighting in April 2023 led to electricity instability and fuel shortages for generators, threatening the central cold chain that holds millions of vaccine doses. Health workers often rely on insulated cold boxes with ice packs or monitor vaccines meticulously, limiting travel distances and time spent in communities due to the weight, storage constraints, and return time limits.

To address these difficulties, vaccine vial monitors and controlled temperature chains have been introduced. The vaccine vial monitor is a heat-sensitive label that changes color when exposed to heat, indicating potential incompatibility. The controlled temperature chain allows specific vaccines to be temporarily kept outside the standard 2°C–8°C range before administration, with monitoring to ensure quality.

A new fridge-free version of the tetanus-diphtheria vaccine, SPVX02, utilizing trehalose to protect it during freeze-drying, has shown promising results in a recent human trial. Stable at temperatures up to 30°C for 24 months, this formulation demonstrated good safety and immunogenicity, albeit requiring further studies in diverse populations and regulatory approvals.

Nevertheless, the fridge-free technology is not yet ready for widespread use in African immunization programs. Larger trials with diverse populations are necessary before considering full-scale implementation. If successful, fridge-free vaccines could enhance flexibility in vaccine delivery, potentially benefiting other temperature-sensitive medicines.

However, Africa already boasts precedents, such as the MenAfriVac meningitis A vaccine, which was prequalified for use under controlled temperature conditions before administration. Other vaccines, including human papillomavirus, typhoid, and cholera vaccines, have also been prequalified for controlled temperature chain use.

The fridge-free approach seeks to eliminate refrigeration during prolonged storage and distribution, but it does not eliminate logistical challenges entirely. Countries might continue to use mixed systems with different handling protocols for years. The real impact may stem from improved last-mile outreach rather than the complete elimination of cold storage in facilities.

Ultimately, the significance of this breakthrough will lie in its ability to extend vaccine coverage to more people, particularly in challenging settings, while addressing safety, feasibility, acceptability, costs, waste, and equity.