New Identity Assay Simplifies Process to Identify Polysaccharide Pneumococcal Serotypes in Vaccines


Investigators optimized the assay during development and qualification to be used in the clinical setting for pneumococcal conjugate vaccines.

Investigators have developed an identity assay, an automated capillary western system, to help determine polysaccharide serotypes. The assay was optimized during development and qualification to be used in the clinical setting for pneumococcal conjugate vaccines (PCV), according to results of a study published in the Journal of Pharmaceutical and Biomedical Analysis.1

Doctor hands making a vaccination in the shoulder of patient | Image Credit: fotofabrika -

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According to the CDC, there are 2 types of pneumococcal vaccines that are recommended in the United States: PCVs and pneumococcal polysaccharide vaccines (PPSV).2 For those younger than 6, PCV15 and PCV20 are recommended by the CDC while those aged 2 through 18 years who have certain risk conditions may require more vaccines against pneumococcal disease. For adults aged 65 years and older or aged 18 years through 64 years with certain risk conditions, PCV15 and PCV20 are both recommended. However, with PCV15, PPSV23 should be a follow up dose, according to the CDC.2

The study authors stated that PCVs are very complex, requiring rigorous analytical testing including release, stability, and characterization of the vaccine.1 They added that the polysaccharide antigen should be conjugated with a protein, such as CRM197, to help boost the T-cell dependent response, which is what makes the PCVs complex. The tests are documented by the WHO, with required identity testing for each polysaccharide and protein carrier, according to the study authors. The identification should be performed for monovalent polysaccharide conjugate bulk and final container of all different types.1

3 Key Takeaways

  1. Researchers have successfully developed and qualified an identity assay, utilizing an automated capillary western system, to determine polysaccharide serotypes in pneumococcal conjugate vaccines (PCVs).
  2. Traditional methods such as Nuclear Magnetic Resonance are limited, leading to the development of immune-based assays and emphasizes the need for identity testing for each polysaccharide and protein carrier, as per WHO recommendations.
  3. The study introduces the ProteinSimple Wes capillary western system as an innovative solution for identifying polysaccharides in PCVs.

For the identification, the gold standard is nuclear magnetic resonance, which is recommended by the WHO. The study authors said that this method is “not capable of measuring polysaccharides in conjugate with a protein due to the highly complex structure.” Therefore, immune-based assays were developed, including ELISA and dot blot, the investigators said. However, the authors noted both methods are labor intensive and time consuming. Other methods have been created, but the study authors stated that methods are expensive, complex, and not ideal for a quality control environment.1

Investigators therefore developed and qualified a new identity assay specifically for multivalent serotypes of polysaccharides with the CRM197 protein and protein conjugate. The ProteinSimple Wes is a capillary western system, combining common laboratory techniques of sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting, according to the study authors. The system was designed for fast usage, automated operation, and simple technology.1

The study authors said the method was successfully qualified and successfully identified “polysaccharides in monovalent bulk conjugates or [drug substance] during clinical release of the PCV program.” They added that this method identified the specificity of polysaccharides among approximately 30 other potential polysaccharides, according to the results.1

Additionally, the study authors said that the assay for PCVs was faster and simpler than ELISA or the manual dot blot. Furthermore, the developed assay was easy to use and had minimal training needed for operation, making it simple and quick for PCV. The investigators added that the method was accurate and efficient, resulting in the further production and advancements in vaccine research beyond PCVs.1


  1. Deiss A, Loughney JW, Rustandi RR, Vuolo K, Mackey MA. Development and qualification of an automated capillary Western method for the identification of polysaccharide serotypes in pneumococcal conjugate vaccine (PCV). J Pharm Biomed Anal. 2024;238:115788. doi:10.1016/j.jpba.2023.115788
  2. Pneumococcal. Centers for Disease Control and Prevention. September 21, 2023. Accessed January 4, 2024.
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