Figure 3.

‘Single-world’ simulation process (continued). In order to measure the impact of the intervention on the epidemic, we use the PEG (figure 2) to construct two epidemics: one uncontrolled (left), one with intervention (right). We start by setting the actual state (denoted by colouring the whole circle) of each individual at time t₀ to their initial condition, and then changing their state according to the intervention, in this case setting p₂ as vaccinated (dark green). We then prune events between t₀ and t₁: removing inconsistent events and allowing the intervention to stochastically remove events (b,c). We then use those events to determine the actual state of each individual at t₁, allow the intervention to alter that state, then prune inconsistent events again (d,e). We repeat the process for times t₂ (f,g), t₃ (h,i) and so on. This final graph can be used to extract our outcome of interest. Any graphs made from the same PEG represent the results of different interventions in a ‘single world’.