Stability of collapse lyophilized influenza vaccine formulations.

A clear limitation of many liquid vaccines is the obligatory cold-chain distribution system. Therefore, distribution of a dried vaccine formulation may be beneficial in terms of vaccine stability, handling and transport. Collapse freeze-drying is a process which utilizes fairly aggressive but at the same time economic lyophilization cycles where the formulation is dried above its glass transition temperature. In this study, we used collapse freeze-drying for a thermosensitive model influenza vaccine (Pandemrix(®)). The dried lyophilizates were further cryo-milled to engineer powder particles in the size range of approximately 20-80 μm which is applicable for epidermal powder immunization. Vaccine potency and stability were neither affected by high temperature input during collapse lyophilization nor over a storage period of six months. Furthermore, cryo-milled vaccine lyophilizates showed good storage stability of up to three months at high storage temperature (40 °C). This technique can provide a powerful tool for the worldwide distribution of vaccine and for new application technologies such as engineered powder immunization.