RIVM Rapport 172203001
A single-dilution assay can be a valid procedure to demonstrate that a product exceeds the minimal requirement given for potency provided that consistency in production and testing has been proven. Information is presented justifying the use of a single dilution assay based upon quantitative responses for establishing the potency of diphtheria toxoid vaccines. Data of 27 multi-dilution assays on the diphtheria toxoid component of DPT-polio vaccines were retrospectively analysed for consistency in production and testing. Criteria for analysis are given and a protocol for quality assurance of a single dilution assay based upon serology is discussed.