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A method is described for converting a mean serum neutralizing antibody titre after primary vaccination directly into a percentage protection value using a single regression slope. This has advantages over the indirect method in which a potency value is first estimated on the log antigen dose scale before conversion to a percentage protection value, since(More)
An analysis was made of data from potency tests on fifteen batches of monovalent foot-and-mouth disease vaccine, comprising five batches each of type O, type A and type C. Regressions were calculated for the relation of percentage protection (probit) versus log 140S antigen dose and for the serum neutralizing antibody titre (log SN50) versus log 140S(More)
The Permanent Commission of O.I.E. on foot and mouth disease has proposed a series of potency standards for foot and mouth disease vaccines. No totally in vitro assay has yet been developed to satisfy these requirements, and most Control Authorities require a potency assay to be carried out in cattle using challenge with virulent virus. There are various(More)
The use of tests in cattle remains the basis for evaluating the potency of foot and mouth disease (FMD) vaccines intended for use in cattle. To be able to compare different types of potency test it is essential to have a good understanding of how measurable responses in cattle to vaccination relate to one another. In this paper the interrelationships were(More)
Sigmoid saturation curves were fitted to the results of titrations of antiserum to foot and mouth disease virus against homologous and heterologous virus strains. Differentiation of strains was readily evident from the different levels of the homologous and heterologous curves. These differences could be quantified by comparison of the saturation curve(More)
—Experimental data need to be assessed for purposes of model identification, estimation of model parameters and consequences of misspecified model fits. Here the first and third factors are considered via analytic formulations for the distribution of the maximum likelihood estimates. When estimating this distribution with statistics, it is a tradition to(More)
Published models for the timecourse of the immune response are reviewed for their applicability to data from animals that have been injected with killed vaccine. Simple models are required so that statistical fitting procedures become straightforward. A class of models that incorporates the concept of clonal selection has been found useful. Immune memory is(More)