WHO/BS/2019.2369 WHO replacement IS for Tetanus Toxoid for use in Flocculation Test

Overview

We report here the results of a study for the characterization of a preparation of tetanus toxoid (coded 16/302) and its calibration in flocculation (Lf) units. Calibration was performed using Ramon flocculation method, standardised using the 2nd International Standard (IS) for Tetanus Toxoid for use in Flocculation Test (04/150, 690 Lf/ampoule). 16/302 was found to have a unitage of 971 Lf/ampoule based on results from 17 laboratories in 10 different countries. There was good agreement in the results obtained (intra-laboratory GCV ranging from 0% to 7%, interlaboratory GCV 11.7%). Data from accelerated thermal degradation studies showed no temperature dependent loss in activity after storage for 9 months, indicating that the standard is likely to have good long-term stability. Further studies at later time points will be performed post establishment.