Evaluation of the degree of adsorption of vaccine components in diphtheria and tetanus vaccines adsorbed

INTRODUCTION. The degree of adsorption of vaccine components on the adjuvant determines vaccine efficacy. Requirements for the degree of adsorption of antigen in the finished product have not been established by the WHO, whereas they are regulated in the Russian State pharmacopoeia. These differences in requirements limit the comparable quality assessment of DTP vaccines from different manufacturers, and the lack of international standards complicates adequately assessing the quality of a wide variety of vaccines.

AIM. To analyze regulatory requirements and literature data for determining the completeness of adsorption of diphtheria and tetanus toxoids in combined vaccines in order to improve quality control systems and harmonize national requirements with global quality standards.

DISCUSSION. Currently, there are no international requirements for the quality of aluminum hydroxide gel for adsorption or for the degree of adsorption of components of DTP vaccine. Leading global pharmacopoeias establish quality standards for aluminum hydroxide gel used for adsorption; however, no requirements have been developed in the Russian Federation. Manufacturers independently establish requirements for the degree of adsorption of antigen for each product, determining this value at least at the stage of obtaining the adsorbed antigen. This quality indicator may not be included in the specifications for the finished product. There are three main methods for assessing the degree of adsorption. They determine the amount of unbound antigen in the supernatant; their sensitivity and cost vary. Antigen content is expressed in generally accepted flocculation units — Lf (Limit of Flocculation). Domestic vaccines differ from foreign ones in the methods for determining the degree of antigen adsorption and the units used to express the quantitative content of tetanus toxoid. Due to the differences in approaches and units for expressing the degree of adsorption, domestic vaccines are inferior to foreign ones. However, this fact does not indicate the low efficacy of domestic DTP-based vaccines.

CONCLUSIONS. Standardizing aluminum hydroxide gel quality requirements for adsorption, antigen adsorption monitoring methods, and units for expressing quantitative antigen content is crucial for harmonizing pharmacopoeial requirements. Implementing current adjuvant requirements and current antigen adsorption quality control methods will simplify regulatory frameworks for DTP-based vaccines.

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