• Fang Gao, Carolyn Swann, Peter Rigsby, Sjoerd Rijpkema, Kay Lockyer, Alastair Logan, Barbara Bolgiano, and Vi IS Working Group.
• Division of Bacteriology, National Institute for Biological Standards and Control, Blanche Lane, Potters Bar, Hertfordshire, EN6 3QG, UK. Electronic address: Fang.Gao@nibsc.org.
• Biologicals. 2019 Jan 1; 57: 34-45.

AbstractNumerous Vi capsular polysaccharide (Vi PS) conjugate vaccines to protect young children and infants from Typhoid are either licensed or under development. These vaccines are evaluated by laboratory methods to ensure their potency and that quality requirement are met. International Standard (IS) preparations of Vi PS are needed to calibrate and harmonise these assays. Twenty laboratories from 12 countries participated in a collaborative study to evaluate two candidate ISs: Citrobacter freundii Vi PS (NIBSC code 12/244) and Salmonella enterica serovar Typhi Vi PS (16/126). On the basis of returned results and stability profiles, these standards were established by the WHO Expert Committee on Biological Standardization in Oct 2017 as the First WHO IS for C. freundii Vi PS with a content of 1.94 ± 0.12 mg Vi PS per ampoule (expanded uncertainty with coverage factor of k = 2.11 corresponding to a 95% level of confidence) and the First WHO IS for S. Typhi Vi PS with a content of 2.03 ± 0.10 mg Vi PS per ampoule (expanded uncertainty with coverage factor of k = 2.11), as determined by quantitative NMR. The study also showed the ISs are suitable for physicochemical and immuno assays used for the quantitation of the Vi PS component in Vi PS and conjugate vaccines.Copyright © 2018. Published by Elsevier Ltd.

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