Single Radial Haemolysis (SRH)

The Single Radial Hemolysis (SRH) assay is a well‑established serological method for the quantitative assessment of anti‑hemagglutinin (HA) antibodies following influenza vaccination or natural infection. The assay, which has been used and standardized in VisMederi since the company foundation, is applicable primarily to influenza A and B viruses and is officially recognized by regulatory authorities (including the European Medicines Agency (EMA)), as a validated correlate of protection for influenza vaccines. SRH measures complement‑mediated hemolysis induced by antigen–antibody complexes formed between influenza viral antigens embedded in agarose and specific antibodies diffusing radially from serum samples. Following incubation, the zone of hemolysis is visualized and quantified by measuring the area of the hemolytic zone, which is directly proportional to the concentration of functional anti‑HA antibodies present in the serum. Results are expressed as hemolysis area (mm²), with defined threshold values associated with protective immunity.