Thermostabilization of Vaccines by Cryopreservation

For thermostabilization of vaccines that incorporate live eukaryotic organisms (e.g., parasites) or cells, cryopreservation is the preferred and usually only method for long-term storage. Parasites include the unicellular protozoa and multicellular helminths (nematodes, trematodes, and cestodes). The PfSPZ live sporozoite vaccines against malaria are cryopreserved. Additionally, many parasites are transmitted by vectors (e.g., mosquitoes, ticks), and these can be targets for vaccination or used in the production of vaccines. Veterinary live vaccines against bovine babesiosis, East Coast Fever, anaplasmosis, several poultry parasites and some viruses, are cryopreserved. Cellular vaccines comprising activated, cytokine-secreting or antigen presenting cells are stabilized by cryopreservation. Cryopreserved vaccines may be stored short-term in ultralow freezers, but typically are distributed via liquid nitrogen (LN₂) or LN₂ vapor-phase (LNVP) cold chains at below -150 °C.