Viruses, Serums, Toxins, and Analogous Products; In Vitro Tests for Serial Release

We are amending the regulations to provide for the use of in vitro potency tests when conducting immunoassays to determine the relative antigen content (potency) of a serial of inactivated veterinary biological product once immunogenicity is established using host animal tests. Such tests would be conducted using unexpired immunogenic reference preparations and parallel line assays, or other methods which demonstrate linearity, specificity, and reproducibility at least equivalent to the parallel line assay. Firms currently using immunoassays which do not meet the standard in this amendment will have 2 years from the effective date of this final rule to update their filed Outlines of Production. This amendment also changes the title of the section and adds definitions of ``Master reference,'' ``Working reference,'' ``Qualifying serial,'' and ``Immunogenicity'' to the regulations. The effect of this action is to standardize requirements for in vitro immunoassay potency tests for inactivated products which cannot be evaluated on the basis of virus titer or bacterial counts.