Single radial immunodiffusion potency test for standardization of indigenous equine influenza vaccine

Single radial immunodiffusion (SRD) assays were used for measuring the haemagglutinin antigen contents of equine influenza vaccine prepared from an Indian virus isolate. A/Equine-2/Ludhiana/1/87 (H3N8). Five different preparations of the vaccine were standardized by SRD to prepare 913 doses, each containing 20 micrograms HA/ml-1 dose-1. This test also showed influenza virus subtype specificity as no cross reaction was observed between subtype 1 (H7N7) and subtype 2 (H3N8) viruses.