# Explorative Supercooling Technology for Prevention of Freeze Damages in Vaccines
###### Abstract  
Most freeze-sensitive vaccines are stored between 2 \({}^{\circ}\)C and 8 \({}^{\circ}\)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 \(-14\)\({}^{\circ}\)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. Footnote †: journal: Applied  
because temperature damage can irreversibly lessen vaccines' effectiveness and immunogenicity, which often necessitates the destruction of damaged stocks. The World Health Organization (WHO) suggests that all vaccines except the oral polio vaccine be stored in the temperature range from 2-8 \({}^{\circ}\)C [3]. To that end, vaccine storage is generally monitored under strict standards, and vaccines are kept at recommended temperatures for as long as possible. Vaccines are often heat-protected but may suffer greater damage from freezing. Indeed, certain vaccines--but not their diluents--can be stable in subzero temperatures as per manufacturers' and the WHO's guidelines, but freezing is seldom essential and rarely recommended in any case. Vaccines containing aluminum adjuvants are irreversibly damaged when frozen due to the clumping of adjuvants, eliminating the immunological properties of the vaccine [4]. This can be a significant bottleneck in our cold chain, considering aluminum adjuvants are the most common adjuvant type used in human vaccines: diphtheria, tetanus, pertussis, liquid _Haemophilus influenzae_ type b (Hib), hepatitis B, and inactivated poliovirus vaccines are all examples of the aluminum adjuvant type [5]. Today, vaccines are stored in refrigerators or well-insulated cold boxes with deep-frozen ice packs [6]. Deep-frozen ice packs can reach temperatures as low as \(-20\)\({}^{\circ}\)C, which poses a high freezing risk to the vaccines stored in close proximity to these packs. Other common causes of vaccine freezing include inappropriate usage and placement of thermostat containers, misusage of refrigerators, misplacement of vaccines within, and inadequate temperature monitoring. While the WHO provides guidelines to mitigate vaccine freezing--such as conditioning ice packs and monitoring temperatures twice every 24 h--they are often prone to human error or ignored. It was found that during transport, freezing temperatures occurred 35.3% of the time in developing countries and 21.9% of the time during storage [5]. This problem has been well documented; it has been reported that in Mongolia, administration of the hepatitis B vaccine during the winter months is associated with poor vaccination effectiveness [7]. In the United States, regions with a higher percentage of refrigerators with frozen temperatures recorded a higher incidence of pertussis [8].