International standard for tetanus toxoid.

An analysis of results of assays obtained at the Laboratory of Hygiene, Department of National Health and Welfare, Ottawa, Canada, shows that the problem of assaying tetanus toxoids differs with the two test-animals used, the mouse and the guinea-pig. In the mouse, the slopes of dosage-response curves of plain and adsorbed toxoids are clearly not similar, so that separate standards are required for their assay. In the guinea-pig, the slopes of immunization curves for these two types are similar, and one standard should suffice. While a second international standard for adsorbed preparations is not required, laboratories performing these tests are advised to establish separate standards-one for plain toxoid and one for adsorbed.