Quantitative estimation of diphtheria and tetanus toxoids. 6. Use of different antibody titration methods for evaluation of immunogenicity in animals during potency assay of diphtheria toxoid.

Two diphtheria toxoid preparations were compared in potency assays in guinea-pigs using different methods for evaluation of the responses to vaccination. The methods used were the direct skin challenge (Schick test) and ELISA and VERO cell titration of antibodies. The different evaluation methods resulted in the same relative potencies between the toxoids. It was observed that when first-vaccination sera were compared with a second-vaccination serum, the relative antibody concentration depended on whether ELISA or VERO cell titration was used.