Explorative Supercooling Technology for Prevention of Freeze Damages in Vaccines

Abstract

Most freeze-sensitive vaccines are stored between 2 °C and 8 °C upon manufacturing and until they are eventually administered in intermediate vaccine stores and health facilities. This so-called “cold chain” of vaccine distribution is strictly regulated at these specific temperatures to avoid freeze damage. Liquid formulations of particular vaccines (e.g., aluminum-adsorbed tetanus toxoid (TT)) will irreversibly lose their immunogenicity once frozen. Using an oscillating magnetic field (OMF), supercooling can inhibit ice crystal nucleation effectively; water is susceptible to influence by a strong magnetic field, allowing normal water dynamics even in subzero freezing conditions. This recently developed technology—composed of a custom-designed electromagnet unit producing an optimal field strength (50 mT) at a specific frequency (1 Hz)—was successfully used to inhibit the formation of ice crystals in aluminum adjuvant TT vaccines, therefore preventing any visible damage in the vaccines’ microscopic structure. Despite being subject to temperatures far below their freezing point (up to −14 °C) for up to seven days, the TT vaccines showed no freeze damage on physical appearances. Results were further validated using shake tests and light microscopy. As storage and freeze-protection become more critical during times of increased vaccination efforts—particularly against COVID-19—this supercooling technology can be a promising solution to distribution problems by removing concern for temperature abuse or shock-induced freezing.