A reference standard calibrated in International Units (IU) is needed for the in vitro potency assay of hepatitis Avaccines prepared by formalin-inactivation of purified hepatitis A virus grown in cell cultures. Thus, a project waslaunched by the European Directorate for the Quality of Medicines & HealthCare (EDQM) to establish one or morenon-adsorbed inactivated hepatitis A vaccine reference preparation(s) as working standard(s), calibrated against the 1stInternational Standard (IS), for the in vitro potency assay (ELISA) of all vaccines present on the European market.Four non-adsorbed liquid preparations of formalin-inactivated hepatitis A antigen with a known antigen contentwere obtained from 3 manufacturers as candidate Biological Reference Preparations (BRPs). Thirteen laboratoriesparticipated in the collaborative study. They were asked to use an in vitro ELISA method adapted from a commerciallyavailable kit for the detection of antibodies to hepatitis A virus. In-house validated assays were to be run in parallel,where available. Some participants also included commercially available hepatitis A vaccines in the assays, afterappropriate desorption.During the collaborative study, several participants using the standard method were faced with problems with some ofthe most recent lots of the test kits. Due to these problems, the standard method did not perform satisfactorily and ahigh number of assays were invalid, whereas the in-house methods appeared to perform better. Despite this, theoverall mean results of the valid assays using both methods were in agreement. Nonetheless, it was decided to base theassignment of the potency values on the in-house methods only.The results showed that all candidate BRPs were suitable for the intended purpose. However, based on availability of thematerial and on the results of end-product testing, 2 candidate reference preparations, Samples C and D, were selected.Both were fromthe same batch but filled on different days; no statistically significant difference in potency was observed.They were thus combined in 1 single batch. The candidate preparation (Sample C/D) was adopted at the June 2009session of the European Pharmacopoeia (Ph. Eur.) Commission as the Ph. Eur. BRP batch 1 for hepatitis A vaccine(inactivated, non-adsorbed), with an assigned potency of 12 IU/ml for in vitro antigen content assays. Accelerateddegradation studies have been initiated. The preliminary data show that the BRP is stable at the recommended storagetemperature (< -50 °C). The BRP will be monitored at regular intervals throughout its lifetime.
