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 Increased human flow and booster inoculation – Estimating effects of vaccination rate increase and vaccination certificate – Okinawa case
Increased human flow and booster inoculation – Estimating effects of vaccination rate increase and vaccination certificate – Okinawa case
 Date
 2021.09.07
 Researcher
 Setsuya Kurahashi
 Organization
 Graduate School of Business Sciences, University of Tsukuba
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Graduate School of Business Sciences, University of Tsukuba
Summary
1.The number of people staying in downtown areas at 13:00 has a strong influence on the increase and decrease of infections
As a result of statistical estimation of the effective reproduction number by the population staying in downtown areas of Okinawa (Naha Kokusaistreet, Misakicho, Ishigakijima) and the population coming in from outside of Okinawa, it was shown that the population staying in downtown areas at 13:00 and 19:00 and the influx of people from outside the prefecture and the influx of infected people became significant. Especially, the increase and decrease in the population in the downtown areas at 13:00 had a strong effect in the short term.
2.If the number of people staying in downtown areas at 13:00 increases 1.4 times, there is a risk of infections spreading in the spring of 2022
With current vaccination, the risk of diminishing of the preventive effect after 180 days of vaccination cannot be avoided, and there is a possibility that infections will spread to more than 600 people from January to April 2022.
3.The number of infected people can be suppressed to a certain extent by 3rd vaccination (booster vaccination) and the improvement of the vaccination rate
By means of 3rd vaccination (booster vaccination) and the improvement of the vaccination rate of young people (75%), the spread of infections after next spring can be suppressed to some extent (440 people), but with the risk of inflow and the increase in the number of people staying (1.4 times) it is difficult to completely end the infections.
4.In addition to a booster vaccination, use of vaccination certificate can be effective
It may be possible to effectively curb the spread of infections by restricting entries to workplaces, restaurants, and event venues using vaccination certificate. If more than 60% of the total can utilize the vaccination certificates, the number of infected people next spring can be suppressed to about 70.
1.Comparison of the number of positive patients (Okinawa)
(1) Increase in human flow
(2) Increase in human flow + booster vaccination
(3) Increase in human flow + booster vaccination + increase in vaccination rate
(4) Increase in human flow + booster vaccination + vaccination certificate restrictions
1(1) Estimation of the number of positive patients in Okinawa when human flow increases
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31 (equivalent to 2021/7/1521)
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31 (equivalent to 2021/1/1824)
No booster vaccination is given.
*1 Vaccine efficacy for infection prevention becomes 85% after vaccination, 70% after 180 days, 50% after 260 days
*2 Vaccination rate for ages 39 or younger 65%, ages 4059 75%, ages 60 or older 85%
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
1(2) Estimation of the number of positive patients in Okinawa when booster vaccination is performed
・Booster vaccination may be able to suppress the spread of infections in Okinawa after the spring of 2022 to some extent.
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31 (equivalent to 2021/7/1521)
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31 (equivalent to 2021/1/1824)
*1 Vaccine efficacy for infection prevention is maintained at 85~76% by booster vaccination
*2 Vaccination rate for ages 39 or younger 65%, ages 4059 75%, ages 60 or older 85%
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
1(3) Estimation of the number of positive patients in Okinawa when vaccination rate is increased and booster vaccination is performed
・If the vaccination rate increases in addition to booster vaccination, it may be possible to further suppress the spread of infections after the spring of 2022.
・However, it is difficult to completely contain the spread of infection by only vaccination.
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31 (equivalent to 2021/7/1521)
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31 (equivalent to 2021/1/1824)
*1 Vaccine efficacy for infection prevention is maintained at 85~76% by booster vaccination
*2 Vaccination rate for ages 39 or younger 75%, ages 4059 85%, ages 60 or older 90%
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
1(4) Estimation of the number of positive patients in Okinawa when vaccination certificate restrictions and booster vaccination are performed
・By utilizing vaccination certificate restrictions, it is possible that the spread of infections after the spring of 2022 in Okinawa can be effectively contained.
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31 (equivalent to 2021/7/1521)
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31 (equivalent to 2021/1/1824)
*1 Vaccine efficacy for infection prevention is maintained at 85~76% by booster vaccination
*2 Vaccination rate for ages 39 or younger 65%, ages 4059 75%, ages 60 or older 85%
*3 After 9/20, 60% restriction on entries to workplaces, restaurants, and events using vaccination certificates
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
2. Comparison of the number of seriously ill patients (Okinawa)
(1) Increase in human flow
(2) Increase in human flow + booster vaccination
(3) Increase in human flow + booster vaccination + increase in vaccination rate
(4) Increase in human flow + booster vaccination + vaccination certificate restrictions
2(1) Estimation of the number of seriously ill patients in Okinawa when human flow increases
・In Okinawa, there is a risk that the number of seriously ill patients will increase if human flow increases.
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31
*1 Vaccine efficacy for infection prevention becomes 85% after vaccination, 70% after 180 days, 50% after 260 days
*2 Vaccination rate for ages 39 or younger 65%, ages 4059 75%, ages 60 or older 85%
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
2(2) Estimation of the number of seriously ill patients in Okinawa when booster vaccination is performed
・Booster vaccination may be able to suppress the number of seriously ill patients in Okinawa to some extent.
・However, there remains the risk that the number of seriously ill patients will remain at a high level.
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31
*1 Vaccine efficacy for infection prevention is maintained at 85~76% by booster vaccination
*2 Vaccination rate for ages 39 or younger 65%, ages 4059 75%, ages 60 or older 85%
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
2(3) Estimation of the number of seriously ill patients in Okinawa when vaccination certificate restrictions and booster vaccination are performed
・If the vaccination rate increases in addition to booster vaccination, it may be possible to further suppress the increase of seriously ill patients.
・However, it is difficult to completely contain the spread of infection by only vaccination.
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31
*1 Vaccine efficacy for infection prevention is maintained at 85~76% by booster vaccination
*2 Vaccination rate for ages 39 or younger 75%, ages 4059 85%, ages 60 or older 90%
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
2(4) Estimation of the number of seriously ill patients when vaccination certificate restrictions and booster vaccination are performed
・By utilizing vaccination certificate restrictions, it is possible that the increase of the number of seriously ill patients in Okinawa can be effectively suppressed.
a) Until 9/19, the number of people staying in downtown areas at 13:00 is maintained at the equivalent of 8/31
b) After 9/20, the number of people staying in downtown areas at 13:00 is 1.2 times that of 8/31
c) After 9/20, the number of people staying in downtown areas at 13:00 is 1.4 times that of 8/31
*1 Vaccine efficacy for infection prevention is maintained at 85~76% by booster vaccination
*2 Vaccination rate for ages 39 or younger 65%, ages 4059 75%, ages 60 or older 85%
*3 60% restriction on entries to workplaces, restaurants, and events using vaccination certificates
Red: Number of new positives (0 years old or older)
Green: Number of new positives (039 years old)
Blue: Number of new positives (4059 years old)
Purple: Number of new positives (60 years old or older)
Solid line: Measured number / Wavy line: Estimated number
* Numbers are 7day moving averages
Model Settings
1.Infection model by SEIR mathematical model and AI optimization method
The SEIR model, which takes into account population flow and AI technology (evolutionary optimization + quasiNewton method), were used to optimize infection model estimation within and between three age groups (039 years, 4059 years, and 60 years or older). The positive patient influx from outside the prefecture was estimated from mobile spatial statistics data (NTT DOCOMO) and LocationMind xPop*1, and incorporated into the model, and the model was trained from the data from March 1 to August 31, 2021.
2.Estimating circuit breaker strength and vaccination effectiveness
The rate of increase in human flow was set for Delta variant. Setting was that the suppression of human flow will be eased after 9/20.
3.Effects of vaccine and behavior change
The vaccine effect was 57% for the 1st dose, 94% for the 2nd dose for the Alpha variant to prevent the infection, and 0.9 times for the Delta variant.
Measured values are used for changes in the number of effective reproductions and the number of population flows from 3/1 to 8/31. After 9/1, the latest 7day moving average was used, and after 11/1, the latest 2 days and the average of last year's infection change rate were used.
Vaccination rate setting
After 3/5 0.05% of the population (1st measured number of medical staff)
After 3/27 0.032%, 0.033% (number of 1st and 2nd medical staff measurements)
After 4/12 0.069%, 0.030% (1st and 2nd actual measurements of medical staff) 0.01% (1st actual measurement of elderly people)
After 5/4 0.064%, 0.078% (1st and 2nd actual measurements of medical staff) 0.065%, 0.006% (1st and 2nd actual measurements of elderly people)
After 6/1 0.064%, 0.078% (1st and 2nd expected medical staff) 0.08%, 0.065% (1st and 2nd expected elderly)
After 6/21 k/2%, k/2% (1st and 2nd expected medical staff) k/2%, k/2% (1st and 2nd expected elderly) k = 1.0%
After 8/15 1.3%
Diminishing vaccine efficacy
The infection suppression effect was assumed to diminish to 64% (Israel Ministry of Health) after 180 days of the second vaccination. However, as shown on each slide, this simulation uses a slightly optimistic scenario. Since no data was available on immunity effect, it was assumed to be equivalent. (Since there were no data on the number of seriously ill patients by age group, a model was used to estimate the total number of seriously ill patients using data on the number of infected patients by age group.)
・Israeli Ministry of Health https://www.gov.il/en/departments/news/0507202103 https://www.gov.il/en/departments/news/0607202104
*1 "LocationMind xPop" data is data that NTT DOCOMO collectively and statistically processes from mobile phone location information sent with permission from users of applications* provided by NTT DOCOMO. Location information is GPS data (latitude and longitude information) that is measured at a minimum of every five minutes, and does not contain information that identifies an individual. * DOCOMO Map Navi Service (map application, local guide) and some other applications
Model Details
Agespecific Vaccine Effect SEIR Model
Infection Transition Probability by Age
(Propagate from right to left)
Inverse Simulation Model
Y is 0 to 39 years old, M is 40 to 59 years old, and E is 60 years old or older.
Estimation of the infection change rate by the population remaining in Okinawa
Tokyo suburbs individual base model
・The model is expressed by 1348 agents composed of two cities based on the household composition in the suburbs of Tokyo
・Rate of change in Rt from 500 trials was measured based on entry restrictions of 20% to 100% for workplaces, restaurants, and event venues based on use of vaccination certificates
・Number of infected people 20/100,000 (≒ 3,000/Tokyo)
Due to vaccination certificate restrictions, the effective reproduction number Rt has decreased. Since it is not realistic to limit all of them, the simulation was performed in the case of a vaccination restriction rate of 60%.
The name is "Tokyo" because it is based on the household composition in the suburbs of Tokyo, but since it is an abstract model, it can be applied to other cities.