Table 1.

Parameters for the epidemic model for the United Kingdom (UK), the Netherlands (NL), and Japan (JP) and the D614G, B.1.1.7, B.1.351, and R.1 variants.

symbol	unit	value						description	source
		D614G		B.1.1.7		B.1.351	R.1	variant
		UK	NL	UK	NL	NL	JP	region
s	–	0.28	0.27	0.54	0.47	0.07	0.33	selective advantage novel variant	est.a
β0	d−1	0.81	0.80	0.39	0.39	0.33	0.32	infection rate (t < t1)	est.
β1	d−1	0.15	0.12	0.24	0.23	0.25	0.21	infection rate (t1 < t < t2)	est.
β2	d−1	0.21	0.33	0.33	0.39	0.26	–	infection rate (t2 < t < t3)	est.
β3	d−1	–	–	0.13	0.22	–	–	infection rate (t3 < t)	est.
t0	d	54	54	243	243	344	327	initial time	–
t1	d	86.6	82.5	302	296	359	387	first break point β	est.
t2	d	188	181	335	333	396	–	second break point β	est.
t3	d	–	–	370	354	–	–	third break point β	est.
p0	–	0.28	0.37	3.3 × 10−4	–	0.01	4.7 × 10−3	initial mutant frequency	est.b
λ0	d−1	–	–	–	1.9 × 10−3	–	–	per capita infection rate due to travel	est.b
rD	–	105	115	95.6	93.2	94.2	98.5	overdispersion parameter death incidence	est.
rF	–	72.8	68.3	81.9	72.1	75.1	66	overdispersion parameter sequence data	est.
τ	d−1	0.011	0.018	3.6 × 10−3	0.024	3.4 × 10−3	0.019	overdispersion of the process noise	est.
ζ	–	8.2 × 10−6	1.7 × 10−5	4.1 × 10−4	3.7 × 10−4	5.1 × 10−3	3.8 × 10−4	initital fraction infected	est.
ξ	–	–	–	0.06	0.05	0.1	0.1	fraction of the population immune at time t0	38,39${}^{{}^{\mathrm{c}}}$
N	–	66.5	17.4	66.5	17.4	17.4	126	population size (million)	–
1/α	d	3	.	.	.	.	.	mean duration of incubation period	23,40
γ	d−1	1/4	.	.	.	.	.	recovery rate from infectious stage	41,42${}^{{}^{\mathrm{d}}}$
ν	d−1	γ/50	.	.	.	.	.	rate of developing severe infection	43,44${}^{{}^{\mathrm{e}}}$
1/ω	d	12.5	.	.	.	.	.	duration of severe infection	23,40${}^{{}^{\mathrm{f}}}$
δ	–	0.3	.	.	.	.	.	probability of dying from severe infection	43–45${}^{{}^{\mathrm{e}}}$

^aEstimated.

^bFor the Dutch B.1.1.7 model, the initial frequency is fixed to 0. Instead, the variant is introduced due to travel from the UK.

^cMore recent estimates for sero-prevalence in the Netherlands are taken from https://www.rivm.nl/pienter-corona-studie/resultaten.

^dThe generation interval in the SEIHR model with exponentially distributed transition times is equal to 1/α + (γ + ν)⁻¹ ≈ 1/α + 1/γ. Hence, with an average incubation period of 3 days, we need an average infectious period of 4 days to get an average generation time of 7 days.

^eBy taking the probability of developing severe infection equal to 0.02 and the probability of dying from severe infection equal to 0.3, we arrive at a case fatality rate of 0.6%. Our choice is also comparable to mortality rates for ICU patients⁴⁵.

^fThe average time between symptom onset and death is 16.5 days. After subtracting the duration of the infections period (γ + ν)⁻¹ ≈ 1/γ, we get an average duration of severe infection of 12.5 days.