Challenges of immunogenicity assays for vaccines.

Clinical development of vaccines requires a specific set of specialized assays to demonstrate the immunogenicity of the vaccine. Ideally, these assays should measure immune responses that correlate with protection against disease. Antibody responses usually correlates to protection for existing vaccines, but for vaccines currently in development it is not always clear which immune responses confer protection. Developing assays for new-generation vaccines usually requires working with cells, pathogens, antigens or assay controls that are not readily available, or are hazardous materials. Validation of these assays involves many challenges, and validation requirements are not yet fully specified in regulatory guidelines or White Papers. The different requirements for clinical vaccine assays and the related challenges in developing and validating these assays are described in this article. We provide our opinion on how to approach these challenges and how to apply the existing guidelines.