Serology-based potency test for inactivated Newcastle disease vaccines.

Twenty-seven inactivated oil-emulsion Newcastle disease vaccines were tested for potency in chickens. Serum samples from groups given 1/50 dose of vaccine were examined by the haemagglutination inhibition (HI) test and the indirect enzyme-linked immunosorbent assay (ELISA). Good correlations were observed between potency and HI titres and between potency and ELISA absorbance. It is recommended that a serology-based potency test replaces the challenge test, reserving challenge only for those batches of vaccines where a clear pass is not indicated.