WHO/BS/2018.2336 Evaluation of Candidate International Standards for Meningococcal Serogroup W and Y Polysaccharides

Overview

Until the introduction of International Standards for MenC, MenA and MenX polysaccharides, the standardization of measurement of polysaccharide content within these vaccines was problematic. This was due to the variety of methods and standards employed by different manufacturers and control laboratories for use in the physicochemical assays to test polysaccharide or conjugate vaccines. For determining the MenW and MenY polysaccharide content in vaccines, these problems remain. For this study, two candidate International Standards for meningococcal capsular group W (MenW) and Y (MenY) polysaccharides were assessed for their suitability as quantitative standards in various physicochemical assays. The intention is that these standards will be used to standardize the quantification of the respective polysaccharide content in meningococcal polysaccharide (conjugate) vaccines and their intermediate components. Twelve laboratories from eleven different countries participated in the collaborative study of candidate International Standard MenW and MenY polysaccharide preparations (coded 16/152 and 16/206, respectively). Our proposals, on the basis of quantitative (qNMR) data from this study, are 1) candidate standard for MenW polysaccharide (16/152) to be assigned a content of 0.925 ± 0.138 mg MenW polysaccharide per ampoule (expanded uncertainty with coverage factor k = 2.36, corresponding to a 95% level of confidence) and 2) candidate standard for MenY polysaccharide (16/206) be assigned a content of 0.950 ± 0.122 mg MenY polysaccharide per ampoule (expanded uncertainty with coverage factor k = 2.36, corresponding to a 95% level of confidence). In accelerated thermal degradation studies a decrease in molecular size of the polysaccharide was observed after storage of the lyophilized material at 37°C and 56°C. The candidate material stored at lower temperatures, -70°C, -20°C or 20°C, was considered stable. The amount of polysaccharide per ampoule remained consistent under all conditions over a 12- month period. Real time stability and accelerated thermal degradation studies are on-going