key: cord-0681883-c5zs7k26 authors: Tokuda, Y.; Kuniya, T. title: Japan's Covid mitigation strategy and its epidemic prediction date: 2021-05-07 journal: nan DOI: 10.1101/2021.05.06.21256476 sha: 91e6f8d6d5e13cb6a1f368fb78bc4f10c6a523b5 doc_id: 681883 cord_uid: c5zs7k26 The COVID-19 epidemic curve in Japan was constructed based on daily reported data from January 14, 2020 until April 20, 2021. A SEIR compartmental model was used for the curve fitting by updating the estimation per wave. In the current vaccination pace of 1/1000, restrictions (state of emergency in Japan) would be repeated 4 times until the end of next March. In the case of 1/500, another round of restriction would be required in the summer 2021, after which the infection would be mitigated. In the case of 1/250, there would be no need for restriction after the current spring restriction. The scenario of completing the vaccination of 110 million people by the end of March 2020 corresponds to the case of 1/250 in this curve. When considering the likely spread of variant with greater infectiousness (here we assume 1.3 times greater than the original virus), 1/500 pace of vaccination would not be enough to contain it and need several series of restrictions. There are currently several variants of concern that are already spreading in urban areas in this country. In the new stage of the replacement of variants, if the vaccination pace could not be quadrupled from the current pace, Japan could not become a zero covid (zero corona) country at least one year. there would be no need for restriction after the current spring restriction. The scenario of completing the vaccination of 110 million people by the end of March 2020 corresponds to the case of 1/250 in this curve. When considering the likely spread of variant with greater infectiousness (here we assume 1.3 times greater than the original virus), 1/500 pace of vaccination would not be enough to contain it and need several series of restrictions. There are currently several variants of concern that are already spreading in urban areas in this country. In the new stage of the replacement of variants, if the vaccination pace could not be quadrupled from the current pace, Japan could not become a zero covid (zero corona) country at least one year. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. countries that aim for elimination. However, unfortunately, the government COVID-19 committee of Japan keeps mitigation strategy, so-called With-Corona policy (2). In fact, as of April 26, the cumulative deaths per 100,000 people was 7.9 in Japan and it was 3.5, 26, and 158 times greater than those of South Korea, China, and Taiwan, respectively (3). Regarding annual GDP in 2020 compared that in 2019, Japan is projected to have contracted 5.3%, while South Korea shrank only 1% and China expanded 2.3% (4). Moreover, we constructed the COVID-19 epidemic curve ( Figure 1A ) in Japan based on daily reported data from January 14, 2020 until April 20, 2021. The following SEIR compartmental model as in (5,6) was used for the curve fitting. , , , , All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. , and represent the susceptible, exposed, infected and removed/recovered populations at time , respectively. The time unit is a day. , and represent the infection rate, the transition rates from to and to , respectively. As in (5,6), we assumed that 0.2 and 0.1 so that the average incubation and infection period are 1/ 5 (days) and 1/ 10 (days), respectively (7,8). In addition, we set 1 so that each population is the proportion to the total population. As in (5,6), to estimate the infection rate , we assumed that the daily number of newly reported cases in Japan is given by and fitted it to the data (9) to find the best that minimizes the leastsquares error, where denotes the detection rate and denotes the population in Japan. We assumed that 1.26 10 (10) and estimated 0.33 by using a similar procedure as in (6). In this study, to estimate the infection rate , we divided the period January 14, 2020 -April 20, 2021 into the following seven parts (see also the actual data in Figure 1A (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 7, 2021. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 7, 2021. ; https://doi.org/10. 1101 We used three scenarios of vaccination rate: 1/1000 (the current pace), 1/500, 1/250 of unvaccinated persons per day. However, when considering the likely spread of variant with greater infectiousness (here we assume 1.3 times greater than the original virus), 1/500 pace of vaccination would not be enough to contain it and need several series of restrictions ( Figure 1B) . As of May 2021, there are several variants of concern including B.1.1.7. that are already spreading in urban areas in this country. Thus, Japan is not currently a member in the Zero Covid community. In this new stage of the replacement of variants, if the vaccination pace could not be quadrupled from the current pace, Japan could not All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 7, 2021. ; https://doi.org/10.1101/2021.05.06.21256476 doi: medRxiv preprint become a member in the community, in which many countries of East Asia and Western Pacific regions belong to, at least one year. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 7, 2021. ; https://doi.org/10.1101/2021.05.06.21256476 doi: medRxiv preprint Figure 1 A B All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 7, 2021. ; https://doi.org/10.1101/2021.05.06.21256476 doi: medRxiv preprint SARS-CoV-2 elimination, not mitigation, creates best outcomes for health, the economy, and civil liberties A cross-country core strategy comparison in China, Japan, Singapore and South Korea during the early COVID-19 pandemic South Korea limits COVID damage to 1% GDP contraction in 2020 No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted