Studies on the Assay of Smallpox Vaccine

Report 1. Evaluation of Groth's method

Abstract

For the purpose of obtaining a more precise assay for potency of vaccine lymph, . Groth's method described in the “Minimun Requirement of Biologic Products” was reinvestigated.
The result revealed that this method was just able to detect fourfold difference in virus content but absolutely not twofold difference.
However, by use of minimum possible amount of serial dilution of the lymph, such as 0.05 ml in place of 0.2 ml as noted in the Minimum Requirement, a little more minute difference of potency could be traced.
In addition to this, it was established by the present investigation that we are able to detect the minute difference as “twofold”, when the reading of the vaccinial responses on the shaved skin of rabbit was conducted in an early stage, for instance, on the 4th day after the inoculation, independently of 7-day observation period as described in the Minimum Requirement.
In view of these observations, it appears that the Groth's original method, which appears to lay not much stress on the highest dilution capable of causing a positive reaction, as well as the recommendationn by the Commission to take definitely positive reaction in 72 hours following the inoculation of 0.1 ml of 1/1, 000 dilution of lymph, is more adequate as compared with the modified Groth's method as now employed in this country.