Table 1.

Input parameters for a model of COVID-19 disease and testing in Massachusetts

Parameter	Value
Cohort characteristics
SARS-CoV-2 prevalence on May 1, 2020, % a	2.99
Initial age distribution of cohort, % [10]
0-19 years	25
20-59	56
≥60	19
Initial distribution of health states on May 1, 2020, % [11] a
Susceptible	89.38
Latent	0.52
Asymptomatic	0.91
Mild/moderate illness	1.49
Severe illness	0.04
Critical illness	0.02
Recuperation	0.01
Recovered	7.63
Health state transition probabilities, by ultimate stage of disease, daily [12-14,16] b
Asymptomatic
Latent to asymptomatic	0.323
Asymptomatic to recovered	0.099
Mild/moderate
Latent to asymptomatic	0.323
Asymptomatic to mild/moderate	0.394
Mild/moderate to recovered	0.095
Severe	With hospital care	Without hospital care
Latent to asymptomatic	NA	0.323
Asymptomatic to mild/moderate	NA	0.394
Mild/moderate to severe	NA	0.143
Severe to recovered	0.091	0.063
Critical
Latent to asymptomatic	NA	0.323
Asymptomatic to mild/moderate	NA	0.394
Mild/moderate to severe	NA	0.284
Severe to recovered	0.026	0.000
Severe to critical	0.105	0.143
Critical to recuperation	0.049	0.000
Recuperation to recovered	0.161	0.000
COVID-19-related mortality while critically ill, probability, daily [42]
0-19 years	0.00001	0.118
20-59	0.004	0.166
≥60	0.050	0.203
Development of COVID-19-like illness symptoms among susceptible and recovered, probability, daily [42]
Mild/moderate illness
0-19 years	0.00005
20-59	0.00005
≥60	0.00008
Severe illness
0-19 years	0.00032
20-59	0.00036
≥60	0.00053
Critical illness
0-19 years	0.00009
20-59	0.00010
≥60	0.00015
Presentation to hospital care with severe symptoms, probability c	0.80
Test characteristics
Self-screen
Positive result, probability	0.80
PCR test [17,18]
Sensitivity, % d	70
Specificity, %	100
Turnaround time, days	1
Test acceptance, probability
Asymptomatic/mild illness/moderate illness	0.80
Critical/severe illness	1.00
Transmissions
Re
May 1 – May 30	0.9000
By health state, probability, daily [30,43,44] d
Latent	0.0000
Asymptomatic	0.2394
Mild/moderate illness	0.1948
Severe illness	0.0135
Critical illness	0.0107
Recuperation	0.0135
Recovery	0.0000
Transmission reduction after test result, % f	Screen positive	Screen negative
Self-screen
Asymptomatic	0	0
Mild/moderate illness	20	N/A
PCR-based strategies
Asymptomatic	65	0
Mild/moderate illness	65	0
Severe/critical/recuperation f	90	90
Costs (USD 2020)
SARS-CoV-2 PCR assay [20]	51
Hospital bed, daily [21-23]	1,640
Intensive care unit, daily [21-23]	2,680

Abbreviations: PCR, polymerase chain reaction; R_e, Effective reproduction number; USD, United States dollars

^aPrevalence and distributions were derived from model validation and calibration as described in the Supplementary Material.

^bAverage days spent in each health state stratified by clinical disease progression severity are presented in Supplementary Table 1. Health state transitions are shown in Supplementary Figure 2.

^cAssumption; includes those with COVID-19 disease and those with COVID-19-like illness.

^dTest sensitivity is 0% in the latent phase and otherwise does not vary by disease states.

^eDaily transmission rates contribute to R_e.

^fAssumptions for transmission reductions following test result are detailed in the Supplementary Material. In severe/critical/recuperation states, transmission reduction is due to hospitalization and thus is applied to all patients regardless of test result.