Increased human flow and booster inoculation – Estimating effects of vaccination rate and vaccination certificate – Tokyo case

・The number of new positive cases was compared against each of the following conditions: increased human flow in downtown areas of Tokyo at night, start of 3rd vaccination, and vaccination certification restrictions.

・In the absence of restrictions on human flow, a rapid spread of infections is expected after the 2nd half of January next year. The main causes were estimated to be increased human flow at night, the decline of vaccine effect, and the delay of the 3rd vaccination.

・If the 3rd vaccination is limited to health care workers and the elderly, the spread of infection at the beginning of the year may be feared, but if the 3rd vaccination is provided to all age groups, the spread of infection can be controlled to some extent.

・The following 3 points are considered effective control measures.
　・A 3rd vaccination for all age groups, starting with those who have passed 180 days on 12/1 since their previous vaccination
　・Restrictions on entry to workplaces, restaurants, and events based on a 3rd vaccination and vaccination certificate
　・Restrictions on human flow when the number of new positive cases exceeds 1,000 (50% reduction)

Comparison of increased human flow, 3rd vaccination and vaccination certificate restrictions

*1 Increase in the number of people staying downtown at 21:00 = (since 10/8)/(6/25-8/8 period average)
*2 3rd vaccination from 12/1 for those who have passed 240 days on 12/1
*3 Rate of restriction on use for persons without vaccination certificate or proof of negative PCR/antigen test results
*4 The number of people staying at 21:00 restricted at 1,000 positive patients (delay time 14 days)

1st effectiveness, 2nd effectiveness: 33%, 88%
Effect in preventing infection 180 days after the 2nd dose: 66%
Vaccination rate Total population (aged 39 years and younger, aged 40-59, aged 60 and older): 55%, 80%, 90%

*1 Increase in the number of people staying downtown at 21:00 = (since 10/8)/(6/25-8/8 period average)
*2 3rd vaccination from 12/1 for those who have passed 240 days on 12/1
*3 Rate of restriction on use for persons without vaccination certificate or proof of negative PCR/antigen test results
*4 The number of people staying at 21:00 restricted at 1,000 positive patients (delay time 14 days)

1st effectiveness, 2nd effectiveness: 33%, 88%
Effect in preventing infection 180 days after the 2nd dose: 66%
Vaccination rate Total population (aged 39 years and younger, aged 40-59, aged 60 and older): 55%, 80%, 90%

*1 Increase in the number of people staying downtown at 21:00 = (since 10/8)/(6/25-8/8 period average)
*2 3rd vaccination from 12/1 for those who have passed 240 days on 12/1
*3 Rate of restriction on use for persons without vaccination certificate or proof of negative PCR/antigen test results
*4 The number of people staying at 21:00 restricted at 1,000 positive patients (delay time 14 days)

1st effectiveness, 2nd effectiveness: 33%, 88%
Effect in preventing infection 180 days after the 2nd dose: 66%
Vaccination rate Total population (aged 39 years and younger, aged 40-59, aged 60 and older): 55%, 80%, 90%

*1 Increase in the number of people staying downtown at 21:00 = (since 10/8)/(6/25-8/8 period average)
*2 3rd vaccination from 12/1 for those who have passed 240 days on 12/1
*3 Rate of restriction on use for persons without vaccination certificate or proof of negative PCR/antigen test results
*4 The number of people staying at 21:00 restricted at 1,000 positive patients (delay time 14 days)

1st effectiveness, 2nd effectiveness: 33%, 88%
Effect in preventing infection 180 days after the 2nd dose: 66%
Vaccination rate Total population (aged 39 years and younger, aged 40-59, aged 60 and older): 55%, 80%, 90%

*1 Increase in the number of people staying downtown at 21:00 = (since 10/8)/(6/25-8/8 period average)
*2 3rd vaccination from 12/1 for those who have passed 240 days on 12/1
*3 Rate of restriction on use for persons without vaccination certificate or proof of negative PCR/antigen test results
*4 The number of people staying at 21:00 restricted at 1,000 positive patients (delay time 14 days)

1st effectiveness, 2nd effectiveness: 33%, 88%
Effect in preventing infection 180 days after the 2nd dose: 66%
Vaccination rate Total population (aged 39 years and younger, aged 40-59, aged 60 and older): 55%, 80%, 90%

*1 Increase in the number of people staying downtown at 21:00 = (since 10/8)/(6/25-8/8 period average)
*2 3rd vaccination from 12/1 for those who have passed 240 days on 12/1
*3 Rate of restriction on use for persons without vaccination certificate or proof of negative PCR/antigen test results
*4 The number of people staying at 21:00 restricted at 1,000 positive patients (delay time 14 days)

1st effectiveness, 2nd effectiveness: 33%, 88%
Effect in preventing infection 180 days after the 2nd dose: 66%
Vaccination rate Total population (aged 39 years and younger, aged 40-59, aged 60 and older): 55%, 80%, 90%

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 + quasi-Newton method), were used to optimize infection model estimation within and between three age groups (0-39 years, 40-59 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 September 30, 2021.

2.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 (set experimentally against the Delta variant) Measured numbers were used for the changes in the effective reproduction and population flow numbers for 3/1 - 9/30. After 10/1, the latest 7-day moving average was used, and after 10/8, the average for the 6/25-8/8 period was 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%

・Vaccine decline effect
Assumed were a 66% decline at 180 days, taking the simple average of these reports that the vaccine was 64% effective in controlling infection in June 2021 when the Delta variant occurred (Israel Ministry of Health), 78% at 90 days for the Alpha variant (Oxford, Nature), 65.5% at 90 days (NEJM), and declined to 82% at a median of 143 days (US CDC). Booster vaccination is assumed to start on 12/1 from those who have passed 180 and 240 days after the 2nd vaccination, and is assumed to return to the level of vaccine effect immediately after the 2nd dose.
https://www.gov.il/en/departments/news/05072021-03, https://www.gov.il/en/departments/news/06072021-04
Resurgence of SARS-CoV-2 Infection in a Highly Vaccinated Health System Workforce, DOI: 10.1056/NEJMc2112981, The new England journal of medicine
COVID vaccines protect against Delta, but their effectiveness wanes, doi: https://doi.org/10.1038/d41586-021-02261-8 , Nature
Comparative Effectiveness of Moderna, Pfizer-BioNTech, and Janssen (Johnson & Johnson) Vaccines in Preventing COVID-19 Hospitalizations Among Adults Without Immunocompromising Conditions — United States, March–August 2021, CDC vol.70, 17, Sep. 2021

*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

・The model is expressed by 1,348 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 (food and drink is restricted to friend networks)
・Number of infected people 20/100,000 (≒ 3,000/Tokyo)