Figure 6

Hypothetical density distribution of clinical episodes of malaria. The distribution of parasite densities among febrile cases is approximated by a gamma distribution with a mean of 3,000/μl in the unvaccinated group and vaccination reduces both the incidence of fever (25% reduction) and the mean parasite density (30% reduction) among the cohort. A cut-off value of 3,000 parasites per microliter is shown and the shaded area represents the cases which risk being misclassified due to the discrepancy between microscopists.