About Simulations
■In this simulation, economic activities are incorporated into the SIRD model, and the risk of spread of infectious diseases and economic losses are analyzed simultaneously.
■The following parameters and predicted values were used in the simulation. Parameters are estimated before applying the model.
■Parameters
・Relationship between people flow and GDP
・Delta mutation rate (percentage of patients infected with delta variants among those positive)
・Severity rate (percentage of patients with severe symptoms among those who tested positive)
・fatality rate (percentage of deaths among those who tested positive)
・Hospitalization rate (percentage of patients with positive results who are hospitalized)
■Predicted values
・Changes in the number of newly infected patients per day (average number of infected patients from Monday to Sunday)
・Number of vaccinations per day
■Model Details
Fujii and Nakata, “Covid-19 and Output in Japan",
https://covid19outputjapan.github.io/JP/files/FujiiNakata_Covid19.pdf
Important Points
■The number of newly infected patients peaks out at 6,000 per day at the end of September. Then, it is assumed to decrease gradually.
■In the case that the declaration is lifted at the end of October this year, and the social and economic activity will be recovered to pre-Covid crisis level over a six-month period...
■The next wave of infection will be January next year
■In that case, the number of seriously ill patients (both Tokyo and national standards) may be more than double the current capacity
■The economic loss for the next 1 year will be about 2.6 trillion yen
■In the case that the declaration is lifted at the end of December this year, and the social and economic activity will be recovered to pre-Covid crisis level over a six-month period...
■The next wave of infection will be September next year
■In that case, the number of seriously ill patients (both Tokyo and national standards) may exceed the current capacity
■Economic losses will increase by about 1 trillion yen compared to the above case
■In the case that having strong restrictions on the social and economic activity starting this week, and the declaration is lifted in mid-November when the number of hospital beds for seriously ill patients becomes below 50%...
■The next wave of infection will be June next year
■In that case, the number of seriously ill patients (both Tokyo and national standards) may be more than double the current capacity
■Economic losses will increase by about 1.5 trillion yen compared to the above case(The declaration of a state of emergency was lifted at the end of October.)
■The number of deaths in this scenario will decrease if the medical system is not strengthened in the above two scenarios, and it is assumed that the current medical system cannot provide adequate care for critically ill patients and home (overnight) patients whose conditions suddenly change.
■With the assumption that it is possible to properly care in the above two scenarios, the cumulative number of deaths in this scenario will not change significantly
Assumption about future contact rate parameter (Lifting the declaration at the end of October)
β：Infection rate without consideration of people's economic activities
βtilde：Infection rate in consideration of people's economic activities
* The solid vertical black line represents actual values
Assumption about Percentage of Delta Variant (common to all scenarios)
* The solid vertical black line represents actual values
Serious illness rate (common to all scenarios)
*As vaccination progresses, the severity rate will remain at a lower level
*Criterias for severely ill patient
・metropolitan standard: Patients on mechanical ventilation or ECMO
・national standard: Patients requiring intensive care unit (ICU) management, ventilator management, or extracorporeal cardiopulmonary support (ECMO) management
* The solid vertical black line represents actual values
Hospitalization rate assumption (common to all scenarios)
*It is assumed that the hospitalization rate will be lower than before due to the effects of vaccination, etc.
* The solid vertical black line represents actual values
Fatality rate assumption (common to all scenarios)
*It is assumed that the Fatality rate will be lower than before due to the effects of vaccination, etc.
* The solid vertical black line represents actual values
Scenario 1: Lifting the declaration at the end of October this year
*Assumptions other than the parameters shown on pages 4 to 8 are given on page 12.
Note 1: Thin lines are optimistic and pessimistic cases of contact rate, fatality rate, serious illness rate, and hospitalization rate parameters
Note 2: The number of deaths is in the case of all patients are cared properly through the strengthening of the medical system; otherwise, the number could increase significantly
Scenario 2: Lifting the declaration at the end of December this year
*Assumptions other than the parameters shown on pages 4 to 8 are given on page 12.
Note 1: Thin lines are optimistic and pessimistic cases of contact rate, fatality rate, serious illness rate, and hospitalization rate parameters
Note 2: The number of deaths is in the case of all patients are cared properly through the strengthening of the medical system; otherwise, the number could increase significantly
Scenario 3: Strong restrictions on the social and economic activity (the declaration is lifted when the number of hospital beds for seriously ill patients becomes 50%)
*Assumptions other than the parameters shown on pages 4 to 8 are given on page 12.
Note 1: Thin lines are optimistic and pessimistic cases of contact rate, fatality rate, serious illness rate, and hospitalization rate parameters
Note 2: The number of deaths is in the case of all patients are cared properly through the strengthening of the medical system; otherwise, the number could increase significantly
Details
■Fujii and Nakata (2021)： COVID-19 and Output in Japan
■https://covid19outputjapan.github.io/JP/, https://covid19outputjapan.github.io/JP/resources.html
■Assuming that after the state of emergency is lifted, human traffic and the economic activity will be recovered to pre-Covid crisis level over a six-month period
■On the left, the black vertical solid lines (middle and right) are the current time (4th week of August and 5th week of September). The two thin lines are the optimistic and pessimistic cases of the steady-state values of contact rate parameter
■The bottom-right panel is the cumulative number of deaths in one year (including deaths to date) and economic losses over the next year. The middle-right panel is the monthly GDP in the region (details of the estimation method will be explained in a paper to be published in the near future).
■It is assumed that the Alpha variant is 1.3 times more infectious than the conventional variant and that serious illness/fatality rate is 1.4 times higher. It is assumed that the Delta variant is 1.5 times more infectious than the Alpha variant and that serious illness/fatality rate is 1.1 times higher. The ratio of the Delta variant is assumed to currently be 90%
■An increased fatality rate due to the tightening of the medical system is not taken into account here
■Considering the season, the contact rate parameter is 1.1 times the steady-state value for the winter peak and 0.9 times for the summer Trough
■The vaccination pace is expected to be 1.2 million doses per day until the end of August (national equivalent, of which 700,000 doses are for the elderly) and it is assumed that the vaccination pace will gradually decline thereafter. It is assumed that 90% of the elderly wish to be vaccinated and 70% of the non-elderly wish to be vaccinated (80% of those who wish to be vaccinated are assumed to be aged 15 or older, and those under 15 are assumed to be unvaccinated). Vaccine efficacy is consistent with "SPI-M-O: Summary of further modelling of easing restrictions – Roadmap Step 4, 9 July 2021". See Fujii and Nakata (2021) for details of the model
