Figure 5.

Simulations of constant-strength and constant-speed interventions. Constant-strength (a–c) and constant-speed (d–f) interventions are simulated using the renewal equation (see electronic supplementary material for details of simulations). (a,d) Daily incidence of infections caused by the wild-type ($i_{\mathrm{wt}}(t)$, grey) and the variant (i_var(t), coloured). (b,e) Instantaneous reproduction number of the variant ${\mathcal{R}}_{\mathrm{var}}(t)$ calculated using equation (2.2). (c,f) Proportion of incidence of infections caused by the variant on a logit scale. Epidemic trajectories are calculated assuming $r_{\mathrm{wt}}=0\hspace{0.17em}{\mathrm{d}}^{-1}$, δ = 0.1 d⁻¹, $r_{\mathrm{var}}=0.1\hspace{0.17em}{\mathrm{d}}^{-1}$, ${\overline{G}}_{\mathrm{wt}}=5\hspace{0.17em}\mathrm{d}$ and κ = 1/5 for pre-intervention conditions, and then introducing constant-strength and constant-speed interventions on day 30. The pre-intervention ratio between the mean generation interval ${\overline{G}}_{\mathrm{var}}/{\overline{G}}_{\mathrm{wt}}$ is assumed to equal 1.5 (longer), 1 (equal) and 1/1.5 (shorter) for three different scenarios. The constant-strength and constant-speed interventions are identically modelled as illustrated in figure 4.