Fig. 1: Modeling flow chart.
The flow chart illustrates the two-step method for predicting the vaccine effectiveness (VE) of the PCV7 serotypes in PCV13. Beginning with the known serotype-specific IgG concentrations after vaccination with PCV7 (both placebo and active vaccine), simulated reverse cumulative distribution curves (RCDCs) are used, along with the known serotype-specific VE of PCV7 (where VE ≈ 1- (pv/pc)), (pv is the percentage of subjects with antibody levels less than protective antibody concentration (Cp) in the vaccinated cohort, and pc is the percentage of subjects with antibody levels less than Cp in the control cohort) to derive the Cp that makes 1-(pv/pc) agree with reported VE for each serotype in PCV7 (red arrow in the left panel). Then, RCDCs are simulated for the PCV7 serotypes using PCV13 recipients’ serotype-specific PCV immunogenicity data. The Cp values previously derived for these serotypes are used to estimate the VE for those serotypes (see arrows in right panel).
