A vaccine measured with a highly variable assay: rabies.

Manufacturers and regulators are challenged when evaluating stability of vaccines when potency is measured using a highly variable assay. Participants in the IABS Workshop on Stability Evaluation of Vaccines, a Life Cycle Approach, were offered a case study from a series of stability studies of a rabies vaccine, using the NIH potency assay. The case study was introduced with a scenario in which a new manufacturer was to formulate, lyophilize and fill the vaccine from bulk supplied by another manufacturer. The regulatory authority requested that data from the new manufacturer be supplied, to supplement that of the original producer. Participants were asked to answer a series of questions posed by the regulator, and critique the study design and data analysis according to principles described during the workshop.