Table 1.

Summary of model assumptions trialled for norovirus, where each model was fitted to age-specific incidence data in England. Models A0-B20 were taken forward to estimate incidence of norovirus between 2020–2022.

Model	A0	A20	B0	B20	D0	D20	E0	F0
Assumptions
First infection	Always symptomatic	Always symptomatic	Always symptomatic	Always symptomatic	50% asymptomatic	50% asymptomatic	50% asymptomatic	Always symptomatic
Duration of Asymptomatic infectiousness (days)	15	15	20	20	15	15	15	15
Asymptomatic infectiousness relative to symptomatic	0.05	0.05	0.05	0.05	0.05	0.05	0.5	1
Under-reporting assumed in fitted data (%)	0	20	0	20	0	20	0	0
Results
Probability of transmission given a contact (qs)	0.1892696	0.2070616	0.1693301	0.1824529	0.2183579	0.2193598	0.374627	0.1909186
Log-likelihood of age-specific incidence when fitted to data from England [15]	−77.94	−190.03	−72.10	−107.46	−667.77	−850.36	−1458.08	−1454.57
R0 (at endemic equilibrium)	1.81	2.03	1.81	2.01	1.94	1.62	>10	>10
Shedding prevalence (at endemic equilibrium) (%)	0.18	0.25	0.303	0.41	0.718	0.70	59.44	59.77
Sero-prevalence (at endemic equilibrium) (%)	24.64	30.55	24.54	29.92	27.73	37.80	20.49	20.17
Comments	Good fit; used for 2020–2022 projections	Good fit; used for 2020–2022 projections	Good fit; used for 2020–2022 projections	Good fit; used for 2020–2022 projections	Poor fit to data, incidence in younger ages was under-estimated and incidence in older ages was over-estimated	Poor fit to data, incidence in younger ages was under-estimated and incidence in older ages was over-estimated	Poor fit to the incidence data (high incidence in adults) and unrealistic R0, but better comparison with expected seroprevalence and shedding	Poor fit to the incidence data (high incidence in adults) and unrealistic R0, but better comparison with expected seroprevalence and shedding