Figure 14: Herd immunity threshold and epidemic final size with gamma distributed susceptibility and exposure to infection.

Curves generated using models (9)–(11) (dark tones) and (17)–(19) (light tones) with approximate ${\mathcal{R}}_0=3:$ herd immunity threshold given by (14) and (22) (black and grey, respectively); final size of unmitigated epidemics given implicitly by (28) and (29) (blue). Vertical lines indicate coefficients of individual variation from the literature and this study: susceptibility to SARS-CoV-2 (black) (England and Scotland 1.48, this study Table 1); connectivity for SARS-CoV-2 (grey) (England and Scotland 1.12, this study Table 1); connectivity (solid orange) (mean 0.93, standard deviation 0.19, as reviewed in Section 5.4.1); infectivity for SARS-CoV-2 (dashed orange) (Hong Kong 2.09 [Adam et al. 2020]); infectivity for SARS-CoV-1 (dashed red) (Singapore 2.62, Beijing 2.64 [Lloyd-Smith et al. 2005]).