Enzyme-Linked Immunosorbent Assay (ELISA) Avidity

The ELISA‑based IgG avidity assay is a well‑established method for assessing the qualitative strength of antigen‑specific antibody responses induced by vaccination or natural infection across multiple vaccine platforms. The assay is applicable to vaccines based on recombinant proteins, viral vectors, inactivated viruses, and mRNA technologies and provides information on antibody maturation that complements quantitative serological endpoints. Antibody avidity is measured by evaluating the resistance of antigen‑specific IgG antibodies to dissociation following exposure to a chaotropic agent. Serially diluted serum samples are incubated on antigen‑coated microplates and treated or untreated with the chaotropic solution, followed by standard ELISA detection. The avidity index is defined as the percentage ratio of antibody binding in treated versus untreated wells and is used to categorize antibody responses according to predefined avidity thresholds. VisMederi has optimized its own assay to investigate avidity of influenza (Comparative analysis of influenza A(H3N2) virus hemagglutinin specific IgG subclass and IgA responses in children and adults after influenza vaccination ) and SARS-COV-2 (Antibody Avidity and Neutralizing Response against SARS-CoV-2 Omicron Variant after Infection or Vaccination ) -specific antibodies.