Fig 8. The relative risk reduction, RRR^(2,1)(ξ), of outcome (I): Having superspreading event under control scheme (II) against scheme (I) as a function of the fraction of fixed component (ρ).

In each panel, the dispersion parameter k is fixed at 0.2, the shading region indicates the situation that ξ ≥ 1 − ρ, and the bold red segment highlights the range of ρ from 0.1 to 0.5, which characterizes the feature of COVID-19. In each panel label, ‘R’ is the reproduction number, and ‘reduction in R’ is the relative reduction in reproduction number (ξ). The ‘NB’ in the horizontal axis label stand = s for negative binomial (distribution).