The potency of a biologic product refers to its ability to exert the desired effect in patients in vivo. It’s expressed in units and is the quantitative measure of biological activity based on the attribute of the product which is linked to the relevant biological properties. For vaccines, defining the product potency is more complicated than simply assessing the mass of the active ingredient. The WHO recommends that the selected potency assays should mimic the expected function of the vaccine within humans.
Advantages of potency testing
Measuring potency during early vaccine development has a number of advantages. These advantages include, but are not limited to.
Potency readouts of vaccine assays are usually associated with different methods for data calculation. Alfa Chemistry mainly offers the following three types of potency testing services.
Infectivity may be determined by median lethal dose (LD50) of animals, by number of infected cells in tissue culture (TCID50, cell culture infectious dose 50 [CCID50]), by numbers of plaques or similar measurements. The number of infected animals/cells/plaques is then divided by the dose to result in potency. Potency is expressed in absolute units, so that a reference is not needed. Potency of many conventional vaccines is assessed by this relationship between infectivity and dose.
Relative potency can be determined by parallel-line analysis of a sample to a reference curve. The curves may be related to antibody titers obtained in animals after immunization with different doses of vaccine. Or, curves may be constructed from dilution series of test vials in vitro curves. Potency is determined by the half maximal effective concentration (EC50) or median effective dose (ED50) ratio of sample versus reference curve. More in vitro than in vivo methods use relative potency.
Antigen mass can be determined by biochemical methods such as chromatography or nuclear magnetic resonance (NMR). This approach is used for many polysaccharide vaccines where the antigen dose is predictive of in vivo immunogenicity. Potency is determined either by parallel-line analysis as described above. Or, the antigen mass may be derived by direct interpolation from a reference curve if permitted by regulatory guidelines. Contrary to parallel-line analysis, only a single or few sample dilutions are needed instead of an entire sample curve.
Why choose us
Vaccine efficacy testing is tailored to each vaccine. By utilizing our experienced experts to work with your team, Alfa Chemistry offers you a potency testing service with the highest specificity, accuracy, and sensitivity. If you have any questions related to potency testing of the vaccine, please feel free to contact us. Alfa Chemistry is always your project partner.
Our products and services are for research use only and cannot be used for any clinical purposes.