Thermostabilization of Vaccines by Lyophilization, Spray Drying, and Foam Drying

Vaccines reduce morbidity and mortality, by interrupting transmission of infectious agents and/or reducing the severity of clinical disease. Vaccines can comprise killed organisms, toxins, proteins, RNA, or live immunogens and are mostly stabilized either in liquid culture, by drying, by freezing, or by cryopreservation. The advantage of dry preservation is that this permits storage and transport at higher temperatures compared to liquid, frozen, or cryopreserved vaccines. Dry stabilization methods vary with the immunogen, use of adjuvants and excipients, the anticipated shelf life and the logistics of distribution. Drying techniques include freeze-drying, spray drying, and foam drying. In this chapter, methods to preserve live vaccines developed against viruses and bacteria in the dried state using lyophilization, spray drying, and foam drying are described.