Immunization standards

Determination of total and free saccharide content in liquid formulations: a challenge for laboratories and manufacturers

First WHO-ISS hands-on laboratory training course held in Rome, Italy

WHO-contracted laboratories that perform tests on behalf of the WHO Prequalification Team (PQT) must deal with the time-consuming task of establishing and validating various methodologies for determining the PRP content of the individual liquid vaccine combinations that they have been requested to investigate. Manufacturers face the same challenge.

A group of experts specially convened by WHO therefore recommended that WHO focus on standardization of a test protocol. PQT initiated a small “Hib project”, to identify a test protocol to be applied for quantitative determination of the total and free polyribosylribitol phosphate (PRP) content of the Hib conjugate component of various liquid vaccine presentations (suspension). A test protocol using acidic hydrolysis was identified as being suitable for quantifying the total and free PRP content of DTwP-HepB-Hib vaccine combinations. Additional investigations showed that the test protocol is applicable to all WHO-prequalified vaccine combinations containing a whole-cell pertussis component using either the WHO PRP International Standard or a Ribitol reference standard.

WHO is now offering training on use of a harmonized assay to control the quality of the Hib component in liquid vaccine combinations, to national (control authority) and quality control (manufacturer) laboratories of low-income countries that produce or expect to produce Hib vaccines for WHO prequalification.

Hands-on training real-life experiences and challenges in using the test protocol

The first hands-on-training course in applying the test protocol using high-performance anion exchange chromatography pulsed amperometric detection (HPAEC-PAD) for determining the total and free saccharide content of Haemophilus influenzae type b liquid combined vaccines, was held at the National Centre for Research and Evaluation of Immunobiologicals of the Istituto Superiore di Sanità, Rome (Italy) in late 2014. It involved sample preparation for analysis of total and free saccharide, as well as other critical steps, performed by the trainees themselves. Test outcomes, real-life experiences and challenges in using the test protocol were discussed extensively. Participants should now be able to facilitate implementation of this quality control method at their home institution. Two additional courses are planned and are already fully booked, but further courses will be organized if demand is sufficient.