Table 1.

Parameters list for model fitting.

Parameter	Meaning	Setting	Notes
Si	Population size in the i-th age group	45 million (Bureau of Statistics, 2014)	Fixed
R0	Basic reproduction number	Uniform (3, 4) (Anderson et al., 2020; Sanche et al., 2020; Viceconte and Petrosillo, 2020; Mizumoto et al., 2020)	R0 = 3.5 was used in the heatmap.
$1/\gamma$	Average time from exposure to preclinical symptomatic (pre-symptomatic)	Gamma (θ = 0.1, k = 20) days (Lauer et al., 2020; Backer et al., 2020)	$1/\gamma$ = 2 days was used in the heatmap
$1/\delta$	Average time from preclinical symptomatic to clinical symptomatic	Gamma (θ = 0.2, k = 20) days (Kong et al., 2020; Wei et al., 2020)	$1/\delta$ = 4 days was used in the heatmap
$\theta$	Average time from clinical symptomatic to recover for those quarantined	20 days (Deng et al., 2020)	Fixed (No influence on model fitting)
$cnt{1}_{ij}$	Social contact from j-th to i-th age groups before the outbreak		From surveys (Zhang et al., 2020; Zhang et al., 2019)
$cnt{2}_{ij}$	Social contact from j-th to i-th age groups during the outbreak		From surveys (Zhang et al., 2020; Zhang et al., 2019)
p	The proportion of exposure get quarantined (contact tracing)	Range: (0, 0.8)	Fitted by the data
$\epsilon$	Case isolation speed (days), from clinical symptomatic to remove for those not in quarantined	Range: (1, 15) days	Fitted by the data
a	Parameter of the sigmoid function	Uniform (0.5, 1.5)	a = 1 was used in the heatmap
b	Parameter of the sigmoid function	Uniform (17, 20)	b = 19 was used in the heatmap
scnt1	Scale parameter of social contact before the outbreak	Range: (0.9, 1.3)	Fitted by the data; final social contact = $\text{s}\text{c}\text{n}\text{t}1\text{*}cnt{1}_{ij}$
scnt2	Scale parameter of social contact during the outbreak	Range: (0.9, 1.3)	Fitted by the data; final social contact = $\text{s}\text{c}\text{n}\text{t}2\text{*}cnt{2}_{ij}$