Single radial immunodiffusion assays for the standardization of the antigenic content of rabies vaccines.

: The method currently recommended for the assay of rabies vaccine potency is a mouse protection test, the NIH test. It is widely accepted that the estimates of potency obtained in such tests are imprecise. We have applied the single radial immunodiffusion (SRD) technique to the assay of the glycoprotein antigen, the major protective antigen of the rabies virion. In this paper we have summarized the results of an international collaborative study, in which SRD was shown to give reproducible estimates of glycoprotein content. In addition the use of SRD in assessing the stability of rabies vaccines is discussed.