Thin-Film Freeze-Drying Is a Viable Method to Convert Vaccines Containing Aluminum Salts from Liquid to Dry Powder.

Aluminum salts are used as an adjuvant in many human and veterinary vaccines. However, aluminum salt-adjuvanted vaccines are sensitive to temperature change and must be stored at 2-8 °C. Inadvertently exposing them to slow freezing temperatures can cause irreversible aggregation of aluminum salt microparticles and loss of potency and/or immunogenicity of the vaccines. There have been efforts to overcome this limitation by either adding stabilizing agents to the liquid vaccine or converting the vaccine from a liquid to a dry powder. Thin-film freeze-drying (TFFD) has proven to be an effective process to convert aluminum salt-adjuvanted vaccines from liquid to dry powder without causing particle aggregation or loss of immunogenicity upon reconstitution. This chapter provides a review of the TFFD process and examples for preparing stable aluminum salt-adjuvanted vaccine dry powders using TFFD.