FIG. 3.

PP activity against meningococcal bacteremia in an ex vivo model using human blood. The results are shown for individual pre- and postimmunization sera from the 36 adults immunized with three doses of the meningococcal recombinant protein vaccine. Each symbol represents the mean from two to three assays. The dashed lines represent a −0.5 log₁₀ change, the threshold considered positive in the assay (see Table 2). Against strain NZ98/254, 11% of the preimmunization sera were positive for PP, and this proportion increased to 61% after immunization (P < 0.001). For strain S3032, the proportions of sera with PP activity before and after immunization were 42% and 94%, respectively (P < 0.001).