Standard Statistical Methods for Immunogenicity Data
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In this chapter, the four standard statistics to summarize humoral and cellular immunogenicity data—the geometric mean response, the geometric mean fold increase, the seroprotection rate and the seroconversion rate—are introduced. For each of these summary statistics, the standard statistical analysis is covered in great detail, both for single vaccine and comparative vaccine trials. A persistent misconception about the geometric mean fold increase and baseline imbalance is ironed out. The analysis of rates (i.e. proportions) receives extensive treatment, because binary immunogenicity and safety endpoints are very common in clinical vaccine research. A simple but very effective bias correction for the rate ratio is brought to the attention of the reader. Superior performing alternatives to the conventional methods for comparing two rates are given a prominent place. It is explained how exact confidence intervals for a risk difference or a relative risk can be obtained. The reverse cumulative distribution plot, an intuitively pleasing and useful graphic tool to display immune response profiles, is exemplified. Statistical tests that can be applied to compare reverse cumulative distribution curves are presented.