Application of a Statistical Method for the Design of Potency of Smallpox Vaccine

A statistical method for the determination of dilution factor of bulk suspension to build up final smallpox vaccine, which must be certified with maximal probability not to go under the legally predetermined level of potency, is proposed. The principle lies in the use of the probability paper for statistical analysis. 1) Preliminary experiments show that the logarithmic values of estimated PFU (pock-forming units) of one test material are normally distributed. And the standard deviation σ. which is considered consistent to other samples, is estimated. 2) Suppose we get a potency titer m(=log PFU) of the bulk suspension at one trial, dilute it a times with suitable dilution factor, then the second titration is made about this diluted suspension. It is theoretically induced that the second estimate is normally distributed with parameters N (m―log a,(√<2>σ)^2). 3) A target point for determining the dilution factor is determined by drawing a line on the probability paper which passes the point (5%, at legal level) and has the inclination angle that corresponds to √<2>σ. Crossing on the abscissa is the target point. 4) The second estimates of many samples are plotted. An experimental distribution line thus obtained shows a good coincidence with that theoretically preformed in the section 3)