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
Analysis
■Quantitative analysis of the impact on infection and the economy by strong restrictions on the social and economic activity comparable to lockdown in Tokyo
■Assuming that the lockdown begins on August 30
■Assuming that the lockdown causes a reduction in human traffic and economic activity comparable to that caused by the declaration of the first state of emergency
■Assuming that the lockdown will be lifted when the number of hospital beds for seriously ill patients (Tokyo and national standards) both reaches 80% / 50% of the current number of secured beds
■Assuming that human traffic and economic activity will be gradually recovered to pre-Corona crisis level over a six-month period after the lifting of the lockdown
■The increase in the human traffic right after the lifting of the lockdown is set as somewhat higher than the increase at the lifting of declaration
■Considering the psychological impact of a small number of newly infected and seriously ill patients would continue after the lifting of the lockdown
→Based on the above assumptions, we applied the model described on page 2 to analyze the impact of lockdown on infection and the economy (Scenarios without lockdown are also described for comparison.).
*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
■Results
■The lockdown will be lifted in the second week of October (80% case) / the second week of November (50% case)
■Compared to the basic scenario (no lockdown, lifting the declaration in mid-October, strengthening medical system)...
■The cumulative number of deaths increases by about 100 / decreased by about 100
→There is no significant increase or decrease as the vaccination progresses.
■Economic losses increases over the next year by about 1.5 trillion yen(80% case) / about 2.5 trillion yen(50% case)
(over the next year: Tokyo's annual GDP is about 100 trillion yen)
■Important Points
■Lockdown requires large economic costs
■Whether the cumulative number of deaths increases or decreases depends on people’s behavior after the lifting of the lockdown
■Lockdown could delay the next wave of infection by 2-4 months
■The next wave of infection will be bigger than the case without the lockdown
■Because the next wave of infection will occur with relatively few people gaining immunity from being infected
Basic scenario (no lockdown, about 4,000 newly infected patients per day at the time of the lifting of emergency declaration in mid-October)
* The solid vertical black line represents actual values
Note 1: Thin lines are optimistic and pessimistic cases of contact rate parameter, 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
Lockdown scenario: lifting the lockdown when the utilization rate of hospital beds for seriously ill patients reaches 80%
* The solid vertical black line represents actual values
Note 1: Thin lines are optimistic and pessimistic cases of contact rate parameter, 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
Lockdown scenario: lifting the lockdown when the utilization rate of hospital beds for seriously ill patients reaches 50%
* The solid vertical black line represents actual values
Note 1: Thin lines are optimistic and pessimistic cases of contact rate parameter, 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 and the lockdown will be lifted, human traffic and the economic activity will be restored to pre-Covid crisis level over a six-month period
■On the left, the black vertical solid line (right) is the current time (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
