A Classical Parallel Line Interlot Potency Comparison of Lots 10 and 15 of Rift Valley Fever Vaccine in an Animal Model

Abstract : Twenty lots of an improved formalin-inactivated Rift Valley fever vaccine were prepared in 1978-1979 with well-characterized, diploid fetal rhesus lung cells. Human tests of this new vaccine revealed lot to lot variability in serological response. The plaque-reducing neutralization test was used in a classical parallel line bioassay to measure the difference between the potency of lot 12 and lot 15 in Wistar Furth rats. A twofold difference in potency was detected using minimal resources. The size of the experiment was done by two separate methods, involving sequential and randomized assignment of sera to the neutralization tests. The sequential assignment gave a better estimate of the within-lot dose response. The randomized determination eliminated confounding the between-lot variability with drift in the neutralization test, but at a cost of loss of some of the discernible effect of lot and dose on response. Keywords: Test and Evaluation, Medical research.