Quantitative estimation of diphtheria and tetanus toxoids. 3. Comparative assays in mice and in guinea-pigs of two tetanus toxoid preparations.

Two freeze-dried international reference tetanus toxoids of different origin and purified by different methods were compared in various potency assay systems, in vitro as well as in vivo. When the antigenic contents in the two toxoids are used as the basis for expressing the relative potency, different tests in animals gave different potencies. It is concluded that, as a result of such differences, tetanus vaccines can hardly be quantitated unambiguously in potency assays in animals. Since, however, a biological immunogenicity control seems necessary, a more simple type of test is suggested, which will require much less resources in terms of animals and manpower.