Figure 5.

Percent error associated with vaccine efficacy increases as vaccine efficacy increases. Plot shows results for 100 and 1,000 individuals per arm.

$VE=1-\frac{{\overline{D}}_V}{{\overline{D}}_{UV}}$

${\overline{D}}_V$ is the mean density in the vaccinated group and ${\overline{D}}_{UV}$ is the mean density in the unvaccinated group. The frequency of densities in a cohort is described by a gamma distribution with a mean density of 3,000 parasites per microliter in the unvaccinated group and 1,500 parasites per microliter in the vaccinated group. Error associated with each density measurement is calculated using the error model in Figure 4 and propagated in the calculation of vaccine efficacy using standard error propagation methods.