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
■Optimistic Scenario: Over the next few months, if the number of new infections per day in Tokyo is expected to hover around 4,000 to 8,000...(p.9)
■Under the current COVID-19 care system, the number of severely ill patients (both Tokyo and national standards) is likely to continue at a level that exceeds the current capacity in the short and long term
■Inpatient beds may be over capacity even if "asymptomatic, mildly ill, (possibly moderately ill 1) are treated at home or in overnight care"
■If the COVID-19 medical system can be strengthened to properly care for patients who are seriously ill or whose condition suddenly changes at home (overnight), the average number of deaths per day is likely to remain below 5
■If not, the number of death could rise significantly
■Pessimistic Scenario: Over the next few months, if the number of new infections per day in Tokyo is expected to hover around 8,000 to 10,000...(p.10)
■Under the current COVID-19 care system, the number of severely ill patients (both Tokyo and national standards) is likely to continue at a level significantly higher than the current capacity, both in the short and long term
■Inpatient beds may be far beyond capacity even if "asymptomatic, mildly ill, (possibly moderately ill 1) are treated at home or in overnight care"
■If the COVID-19 medical system can be strengthened to properly care for patients who are seriously ill or whose condition suddenly changes at home (overnight), the average number of deaths per day is likely to remain below 10
■If not, the number of death could rise significantly
Assumption on Delta variant percentages (common to both scenarios)
The proportion of delta-type mutants is assumed to reach about 90% at week 1 of August.
*The solid vertical black line represents actual values
"Contact interval parameter
* The solid vertical black line represents actual values
Assumptions on severe illness rate (common to both 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
Assumptions on hospitalization rate, and fatality rate (common to both scenarios)
*It is assumed that the death rate and hospitalization rate will be lower than before due to the effects of vaccination, etc.
*The solid vertical black line represents actual values
GDP / Human flow data
People flow based on COVID-19's Community Mobility Report. GDP is estimated from monthly data such as the Industrial Property Index (IIP) and the Third Industrial Activity Index
Optimistic scenario: Suppressing the spread of infection via voluntary behavioral change
The number of critically ill patients (Tokyo/national standard) may exceed the current acceptance capacity
Assumptions other than the model parameters shown on pages 4 to 8 are as follows
*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
*Assumption of the number of new infections (Optimistic):The number of new infections reached 6000 in mid-August and then declined
*Projected vaccination rate is assumed to be 1.2 million vaccinations per day (Nationwide conversion: 700,000 bottles for the elderly) then assume a gradual decline (common to both scenarios)
* See page 11 for a detailed explanation
Pessimistic scenario: Suppressing the spread of infection via voluntary behavioral change
The number of critically ill patients (Tokyo/national standard) and hospitalized patients may exceed the current acceptance capacity
Assumptions other than the model parameters shown on pages 4 to 8 are as follows
* 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
*Assumption of the number of new infections (Pessimistic):The number of new infections reached 10,000 in mid to late August and then declined
* Projected vaccination rate is assumed to be 1.2 million vaccinations per day (Nationwide conversion: 700,000 bottles for the elderly) then assume a gradual decline (common to both scenarios)
* See page 11 for a detailed explanation
Controlling the spread of infection by via voluntary behavioral change (Details)
■The figure presents a scenario wherein we are unable to take the additional measures in order to suppress future infections. The infection spreads, and people voluntarily modify their behavior due to the strain on medical care.
■For further information on research into voluntary behavior modification in Japan, refer to Watanabe and Yabu (2021): Japan's Voluntary Lockdown: Further Evidence Based on Age-Specific Mobile Location Data.
■The black vertical solid lines to the left (middle and right) indicates the present point in time (4th week of August and 5th week of September). The two narrow blue lines show where the parameters we have estimated (relationship between human flow andGDP, contact intervals, case fatality rates, rates of cases that become severe, and hospitalization rates) are 2 standard deviations away from their respective point estimates.
■The bottom-right panel shows the total death toll after 1 year (including the death toll thus far) and the future economic losses in 1 year. The middle-right panel shows the regional monthly GDP (we will explain the details of how we made our estimates in an article that will be published in the near future).
■We assume that the infectious capacity of the Alpha variant is 1.3 times that of the conventional strain, and that the rate of cases that become severe and case fatality rate will be 1.4 times that of the conventional strain. We assume that the infectious capacity of the Delta variant is 1.5 times that of the Alpha variant, and the rate of cases that become severe / case fatality rate will be 1.1 times that of the Alpha variant. We assume that the Delta variant proportion is currently 90%.
■We assume that the number of newly infected individuals will continue to rise in the next 2 to 3 weeks, and then will subsequently go down.
■An increased mortality rate due to the tightening of the medical system is not taken into account here.
■For our perspective on the pace of vaccination, we estimate that by the end of August, there will be 1.2 million units of vaccines administered each day (national conversion; of this amount, the elderly populace will use 700,000 units per day), then there will subsequently be 900,000 units per day. We estimate that of those who want to get vaccinated, 90% will be elderly and 70% will be non-elderly (assuming 80% will be those age 15 or older who want the vaccine, and those younger than 15 will be unvaccinated). The effects of the vaccines are consistent with “SPI-M-O: Summary of further modelling of easing restrictions – Roadmap Step 4, 9 June 2021.” For details about the model, please refer to Fujii and Nakata (2021).
MODELS WE ARE USING
■Epidemiological macro model
■Fujii and Nakata (2021): Covid-19 and Output in Japan
■ https://covid19outputjapan.github.io/JP/, https://covid19outputjapan.github.io/JP/resources.html
■Adding economic activity to a simple epidemiological model in a simple way
■Reference materials: “Policy analysis and proposals based on economic models”, “Policy analysis and proposals based on simple models”
■The calculation, “If future economic activity has this profile, the number of infected individuals and the number of severe patients will have this profile”
■The calculation based on an epidemiological model, “If future effective reproduction numbers have this profile, the number of infected individuals and the number of severe patients will have this profile”
■Estimates from past data on “the relationship between human flow and infection” and “the relationship between human flow and economic activity”
■Simultaneous analysis of “Corona infection and economic activity”
■Presentation of mid- to long-term perspectives
■Considering the profile of the Delta variant proportion thus far and in the future
■Considering the profile of vaccinations thus far and in the future
■Adjusting parameters to consider how vaccination of the elderly will start to reduce the overall rate of cases that become severe and case fatality rates, and how the transition of infections primarily to the young will start to elevate the contact interval
