Abstract:
INTRODUCTION : Before release, vaccine batches are assessed for quality to evaluate whether they meet
the product specifications. Vaccine batch tests, in particular of inactivated and toxoid vaccines, still
largely rely on in vivo methods. Improved vaccine production processes, ethical concerns, and suboptimal
performance of some in vivo tests have led to the development of in vitro alternatives.
AREAS COVERED : This review describes the scientific constraints that need to be overcome for replacement
of in vivo batch tests, as well as potential solutions. Topics include the critical quality attributes of
vaccines that require testing, the use of cell-based assays to mimic aspects of in vivo vaccine-induced
immune responses, how difficulties with testing adjuvanted vaccines in vitro can be overcome, the use
of altered batches to validate new in vitro test methods, and how cooperation between different
stakeholders is key to moving the transition forward.
EXPERT OPINION : For safety testing, many in vitro alternatives are already available or at an advanced
level of development. For potency testing, in vitro alternatives largely comprise immunochemical
methods that assess several, but not all critical vaccine properties. One-to-one replacement by
in vitro alternatives is not always possible and a combination of methods may be required.
