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This paper estimated the impact of intervention effects (state of emergency (SOE) or quasi-SOE requirements) and information effects (publicized increases in the number of coronavirus disease 2019 (COVID-19) deaths and fear of infection) on preventive behaviors and telecommuting during the COVID-19 pandemic using the Japan Household Panel Survey. Our results indicated that SOEs and quasi-SOEs had positive effects on the adoption of preventive behaviors among individuals, including handwashing, which indicates that an SOE has a direct effect and an indirect effect. Although SOEs in Japan were less enforceable and more lenient than those in other countries, they still had a certain effect on people's adoption of preventive behaviors. However, the contribution of information effects was much larger than that of intervention effects, suggesting the importance of how and when information should be communicated to the public to prevent the spread of infection., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Chang, Yamamoto. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Introduction: The emergence of the novel coronavirus disease of 2019 (COVID-19) has led to huge disruptions in the medical field and society. The significance of training and education for experts has been increasingly acknowledged in Japan, where the number of infectious disease (ID) specialists is reportedly insufficient. In this paper, we report the results of a web-based survey that was conducted to reveal the ways in which the COVID-19 pandemic has influenced medical students' awareness of ID specialists and future career choices., Method: This cross-sectional descriptive study was conducted in March 2021 and targeted 717 medical students belonging to Medical School of Okayama University, Japan. The questionnaire consisted of four questions meant to assess students' knowledge and future intentions of becoming ID specialists., Results: We obtained 328 eligible questionnaires (response rate: 45.7%). Of 227 (69.2%) students who were aware of ID specialists, 99 (43.6%) answered that they came to know about them only after the pandemic, 12 (3.7%) answered that their interest in being an ID specialist arose during the pandemic, while 36 (11.0%) responded that they would rather not become ID specialists. At the time of the survey, 5 students (1.5%) were aiming to become ID specialists., Conclusion: We observed a very low rate of interest to be an ID specialist among medical students. The experience of the pandemic does not seem to have influenced Japanese medical students to choose ID as a specialty for their careers. Continuous efforts to increase the number of ID specialists are necessary in Japan as a countermeasure against the coming pandemic., Competing Interests: The authors have declared that no competing interests exist.

Background: In the global aging, the coronavirus disease 2019 (COVID-19) pandemic may have affected the place of death (PoD) in Japan, where hospital deaths have dominated for decades. We analyzed the PoD trends before and during the COVID-19 pandemic in Japan. Methods: This nationwide observational study used vital statistics based on death certificates from Japan between 1951 and 2021. The proportion of PoD; deaths at home, hospitals, and nursing homes; and annual percentage change (APC) were estimated using joinpoint regression analysis. Analyses were stratified by age groups and causes of death. Results: After 2019, home deaths exhibited upward trends, while hospital death turned into downward trends. By age, no significant trend change was seen in the 0–19 age group, while hospital deaths decreased in the 20–64 age group in 2019. The trend change in home death in the ≥65 age group significantly increased since 2019 with an APC of 12.3% (95% confidence interval [CI]: 9.0 to 15.7), while their hospital death trends decreased by −4.0% (95% CI: −4.9 to −3.1) in 2019−2021. By cause of death, home death due to cancer and the old age increased since 2019 with an APC of 29.3% (95% CI: 25.4 to 33.2) and 8.8% (95% CI: 5.5 to 12.2), respectively. Conclusion: PoD has shifted from hospital to home during the COVID-19 pandemic in Japan. The majority of whom were older population with cancer or old age. [ABSTRACT FROM AUTHOR]

Background: The coronavirus disease 2019 (COVID-19) pandemic has put a strain on the healthcare system, and sudden changes in disease status during home treatment have become a serious issue. Therefore, prediction of disease severity and allocation of sufficient medical resources, including high-flow nasal cannula (HFNC), to patients in need are important. We aimed to determine risk factors for the need of HFNC use in COVID-19. Methods: This was a single-center retrospective observational cohort study including all eligible hospitalized adult patients aged ≥18 years diagnosed with COVID-19 between April 14, 2020 and August 5, 2021 who were treated in the study hospital. The primary outcome is the need for HFNC. Nineteen potential predictive variables, including patient characteristics at hospital admission, were screened using least absolute shrinkage and selection operator and logistic regression to construct a predictive risk score. Accuracy of the risk score was determined using area under the receiver operating characteristic curve. Results: The study cohort included 148 patients. The rate of the need for HFNC was 22.9%. Among the 19 potential variables, percutaneous oxygen saturation (SpO2) <92% (odds ratio [OR] 7.50, 95% confidence interval [CI] 2.806–20.82) and IL-6 (OR 1.021, 95% CI 1.010–1.033) were included in developing the risk score, which was termed interleukin (IL)-6-based COVID-19 severity (IBC-S) score. Conclusions: The IBC-S score, an easy-to-use risk score based on parameters available at the time of hospital admission, predicted the need for HFNC in patients with COVID-19. The IBC-S score based on interleukin-6 and SpO2 might aid in determining patients who should be transported to a tertiary medical institution or an isolation facility. [ABSTRACT FROM AUTHOR]

This study aimed to determine the optimal conditions to measure the percentage of the area considered as pneumonia (pneumonia volume ratio [PVR]) and the computed tomography (CT) score due to coronavirus disease 2019 (COVID-19) using the Ziostation2 image analysis software (Z2; Ziosoft, Tokyo, Japan), which is popular in Japan, and to evaluate its usefulness for assessing the clinical severity. We included 53 patients (41 men and 12 women, mean age: 61.3 years) diagnosed with COVID-19 using polymerase chain reaction who had undergone chest CT and were hospitalized between January 2020 and January 2021. Based on the COVID-19 infection severity, the patients were classified as mild (n = 38) or severe (n = 15). For 10 randomly selected samples, the PVR and CT scores by Z2 under different conditions and the visual simple PVR and CT scores were compared. The conditions with the highest statistical agreement were determined. The usefulness of the clinical severity assessment based on the PVR and CT scores using Z2 under the determined conditions was statistically evaluated. The best agreement with the visual measurement was achieved by the Z2 measurement condition of ≥–600 HU. The areas under the receiver operating characteristic curves, Youden's index, and the sensitivity, specificity, and p-values of the PVR and CT scores by Z2 were as follows: PVR: 0.881, 18.69, 66.7, 94.7, and <0.001; CT score: 0.77, 7.5, 40, 74, and 0.002, respectively. We determined the optimal condition for assessing the PVR of COVID-19 pneumonia using Z2 and demonstrated that the AUC of the PVR was higher than that of CT scores in the assessment of clinical severity. The introduction of new technologies is time-consuming and expensive; our method has high clinical utility and can be promptly used in any facility where Z2 has been introduced. [ABSTRACT FROM AUTHOR]

The coronavirus disease 2019 (COVID-19) pandemic provides a unique opportunity studying individual differences in the trajectory of mental distress to relatively homogeneous stressors by longitudinally examining time-course changes between pandemic waves. For 21 months, we tested the effects of COVID-19 waves on mental health among 545 staffs at 18 hospitals treating COVID-19 patients in Shizuoka Prefecture, Japan. Contrary to increasing new infected cases as waves progressed, initially elevated psychological distress (K6) and fear of COVID-19 (FCV-19S) were decreased among waves (K6: B = -.02, 95% confidence interval [CI] = -.03 to -.01; FCV-19S: B = -.10, 95% CI = -.16 to -.04). This initial increase and subsequent decrease in K6 and FCV-19S were more prominent in individuals with high trait anxiety (K6: B = 1.55, 95% CI = 1.18 to 1.91; FCV-19S: B = 4.27, 95% CI = 2.50 to 6.04) and in occupations other than physicians or nurses. The current study revealed time-course changes in psychological distress and fear regarding COVID-19 in each pandemic wave and across waves, and indicated the usefulness of trait anxiety and occupation as predictors of mental health outcomes. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has created an extraordinary situation for undergraduate students. The aim of this study is to evaluate the impact of the COVID-19 pandemic on the national examination for pharmacists in Japan. In this study, we analyzed the content of Twitter to assess the impact of COVID-19 on the national exam, including psychological aspects. Tweets including the words "national examinations" and "pharmacists" were compiled from December 2020 to March 2021. ML-Ask, a python library, was used to evaluate the emotional register of the tweets on the basis of ten elements: Joy, Fondness, Relief, Gloom, Dislike, Anger, Fear, Shame, Excitement, and Surprise. The presence of COVID-19-related terms was clearly visible in tweets about the national examination of pharmacists between December 1st–and 15th, 2020. It was precisely during this period that the government had announced a strategy regarding national examinations, in the light of COVID-19. The analysis found that post December 16th, words associated with negative emotions were mainly related to the examination, but not to COVID-19. As a result of analyzing only infected areas, a relationship between employment and negative feeling was detected. [ABSTRACT FROM AUTHOR]

Background: Despite the worldwide campaigns of COVID-19 vaccinations, the pandemic is still a major medical and social problem. The Ortho VITROS SARS-CoV-2 spike-specific quantitative IgG (VITROS S-IgG) assay has been developed to assess neutralizing antibody (NT antibody) against SARS-CoV-2 spike (S) antibodies. However, it has not been evaluated in Japan, where the total cases and death toll are lower than the rest of the world. Methods: The clinical performance of VITROS S-IgG was evaluated by comparing with the NT antibody levels measured by the surrogate virus neutralizing antibody test (sVNT). A total of 332 serum samples from 188 individuals were used. Of these, 219 samples were from 75 COVID-19 patients: 96 samples from 20 severe/critical cases (Group S), and 123 samples from 55 mild/moderate cases (Group M). The remaining 113 samples were from 113 healthcare workers who had received 2 doses of the BNT162b2 vaccine. Results: VITROS S-IgG showed good correlation with the cPass sVNT assay (Spearman rho = 0.91). Both VITROS S-IgG and cPass sVNT showed significantly higher plateau levels of antibodies in Group S compared to Group M. Regarding the humoral immune responses after BNT162b2 vaccination, individuals who were negative for SARS-CoV-2 nucleocapsid (N)-specific antibodies had statistically lower titers of both S-IgG and sVNT compared to individuals with a history of COVID-19 and individuals who were positive for N-specific antibodies without history of COVID-19. In individuals who were positive for N-specific antibodies, S-IgG and sVNT titers were similar to individuals with a history of COVID-19. Conclusions: Although the automated quantitative immunoassay VITROS S-IgG showed a reasonable correlation with sVNT antibodies, there is some discrepancy between Vitros S-IgG and cPass sVNT in milder cases. Thus, VITROS S-IgG can be a useful diagnostic tool in assessing the immune responses to vaccination and herd immunity. However, careful analysis is necessary to interpret the results. [ABSTRACT FROM AUTHOR]

COVID-19 has brought a great challenge to the medical system. A key scientific question is how to make a balance between home quarantine and staying in the hospital. To this end, we propose a game-based susceptible-exposed-asymptomatic -symptomatic- hospitalized-recovery-dead model to reveal such a situation. In this new framework, time-varying cure rate and mortality are employed and a parameter m is introduced to regulate the probability that individuals are willing to go to the hospital. Through extensive simulations, we find that (1) for low transmission rates (β < 0.2), the high value of m (the willingness to stay in the hospital) indicates the full use of medical resources, and thus the pandemic can be easily contained; (2) for high transmission rates (β > 0.2), large values of m lead to breakdown of the healthcare system, which will further increase the cumulative number of confirmed cases and death cases. Finally, we conduct the empirical analysis using the data from Japan and other typical countries to illustrate the proposed model and to test how our model explains reality. [ABSTRACT FROM AUTHOR]

Objective: To examine the status of food expense insufficiency in Japan during the coronavirus disease 2019 (COVID-19) pandemic and the socioeconomic and sociodemographic factors associated with food expense insufficiency. Design: Food expense insufficiency before and after the pandemic was assessed. The multivariable-adjusted odds ratio (AOR) and 95% confidence interval (CI) were calculated for the association between food expense insufficiency and socioeconomic and sociodemographic factors. Setting: A large-scale, cross-sectional online questionnaire survey. Participants: From August to September 2020, 25,482 participants aged 15–79 years completed the questionnaire (JACSIS 2020 study; Group 1). In October 2020, 917 single parents were surveyed for oversampling purposes. There were 179 single parents in Group 1 and a total of 1096 single parents in Group 2. Results: Group 1 and Group 2 had 747 (2.9%) and 55 (5.0%) participants, respectively, who experienced food expense insufficiency for the first time after April 2020. Young age, part-time employment, being a single parent (in Group 1), and the number of people in the household (five or more in Group 1 and child/children alone in Group 2) were significantly associated with food expense insufficiency. As being a single parent was significantly associated with food expense insufficiency in Group 1 (AOR [95% CI] = 7.23 [5.40–9.68]), we further examined it in Group 2. Single parents who exhibited multiple factors (young age, part-time employment, living only with child/children) were likely to experience food expense insufficiency (15.3–15.8%). Conclusions: Triggered by the pandemic, a small percentage of individuals experienced food expense insufficiency. We identified that factors such as young age, part-time employment, and being a single parent were significantly associated with food expense insufficiency, and discovered that a multiplicity of these factors further increased the risk. Our findings suggest an urgent need to support individuals with a potentially high risk of food expense insufficiency. [ABSTRACT FROM AUTHOR]

An analysis of the national traffic collision trends in Japan for the January 2018 to June 2022 period using existing statistical data indicates that the number of traffic incidents, injuries, and fatalities decreased over time. After the outbreak of COVID-19 in December 2019, traffic volume decreased. In this study, to explore how the COVID-19 pandemic correlates with traffic collisions, we used the Spearman rank correlation of non-parametric statistical test to compare the number of COVID-19 infections with the number of traffic collisions. The number of COVID-19 infections showed a significant inverse correlation with the number of traffic collisions nationwide, in some regions, and in some prefectures. When the number of COVID-19 infections increased, a State of Emergency or Semi-Emergency Spread Prevention Measures were repeatedly declared. We submit that these measures along with the restrictions on the population's autonomy and movement to prevent the spread of infection, reduces the number of traffic incidents, injuries, and fatalities owing to a decrease in traffic volume. Therefore, these lessons learned from the COVID-19 pandemic advocate that regulation of vehicle traffic volume is an effective means of reducing the occurrence of traffic collisions. These results can be applied to future policy development to support road safety improvements during unique events. [ABSTRACT FROM AUTHOR]

Background: Maintaining critical care for non-Coronavirus-disease-2019 (non-COVID-19) patients is a key pillar of tackling the impact of the COVID-19 pandemic. This study aimed to reveal the medium-term impacts of the COVID-19 epidemic on case volumes and quality of intensive care for critically ill non-COVID-19 patients. Methods: Administrative data were used to investigate the trends in case volumes of admissions to intensive care units (ICUs) compared with the previous years. Standardized mortality ratios (SMRs) of non-COVID-19 ICU patients were calculated in each wave of the COVID-19 epidemic in Japan. Results: The ratios of new ICU admissions of non-COVID-19 patients to those in the corresponding months before the epidemic: 21% in May 2020, 8% in August 2020, 9% in February 2021, and 14% in May 2021, approximately concurrent with the peaks in COVID-19 infections. The decrease was greatest for new ICU admissions of non-COVID patients receiving invasive mechanical ventilation (IMV) on the first day of ICU admission: 26%, 15%, 19%, and 19% in the first, second, third, and fourth waves, respectively. No statistically significant change in SMR was observed in any wave of the epidemic; SMRs were 0.990 (95% uncertainty interval (UI), 0.962–1.019), 0.979 (95% UI, 0.953–1.006), 0.996 (95% UI, 0.980–1.013), and 0.989 (95% UI, 0.964–1.014), in the first, second, third, and fourth waves of the epidemic, respectively. Conclusions: Compared to the previous years, the number of non-COVID-19 ICU patients continuously decreased over the medium term during the COVID-19 epidemic. The decrease in case volumes was larger in non-COVID-19 ICU patients initially receiving IMV than those undergoing other initial treatments. The standardized in-hospital mortality of non-COVID-19 ICU patients did not change in any waves of the epidemic. [ABSTRACT FROM AUTHOR]

The suppression of the first wave of COVID-19 in Japan is assumedly attributed to people's increased risk perception after acquiring information from the government and media reports. In this study, going out in public amidst the spread of COVID-19 infections was investigated by examining new polymerase chain reaction (PCR) positive cases of COVID-19 and its relationship to four indicators of people going out in public (the people flow, the index of web searches for going outside, the number of times people browse restaurants, and the number of hotel guests, from the Regional Economic and Social Analysis System (V-RESAS). Two waves of COVID-19 infections were examined using cross-correlation analysis. In the first wave, all four indicators of going out changed to be opposite the change in new PCR positive cases, showing a lag period of –1 to +6 weeks. In the second wave, the same relationship was only observed for the index of web searches for going outside, and two indicators showed the positive lag period of +6 to +12 weeks after the change in new PCR positive cases. Moreover, each indicator in the second wave changed differently compared to the first wave. The complexity of people's behaviors around going out increased in the second wave, when policies and campaigns were implemented and people's attitudes were thought to have changed. In conclusion, the results suggest that policies may have influenced people's mobility, rather than the number of new PCR positive cases. [ABSTRACT FROM AUTHOR]

Background: During the coronavirus disease 2019 (COVID-19) pandemic in Japan, the state of emergency, as a public health measure to control the spread of COVID-19, and the Go To campaign, which included the Go To Travel and Go To Eat campaigns and was purposed to stimulate economic activities, were implemented. This study investigated the impact of these government policies on COVID-19 spread. Methods: This ecological study included all 47 prefectures in Japan as samples between February 3 and December 27, 2020. We used COVID-19 cases and mobility as variables. Additionally, places where social contacts could accrue, defined as restaurants, companies, transportation, and tourist spots; mean temperature and humidity; the number of inhabitants in their twenties to fifties; and the number of COVID-19 cases in the previous period, which were factors or covariates in the graphical modeling analysis, were divided into five periods according to the timing of the implementation of the state of emergency and Go To campaign. Results: Graphical changes occurred throughout all five periods of COVID-19. During the state of emergency (period 2), a correlation between COVID-19 cases and those before the state of emergency (period 1) was observed, although this correlation was not significant in the period after the state of emergency was lifted (period 3). During the implementation of Go To Travel and the Go To Eat campaigns (period 5), the number of places where social contacts could accrue was correlated with COVID-19 cases, with complex associations and mobility. Conclusions: This study confirms that the state of emergency affected the control of COVID-19 spread and that the Go To campaign led to increased COVID-19 cases due to increased mobility by changing behavior in the social environment where social contacts potentially accrue. [ABSTRACT FROM AUTHOR]

Introduction: The novel coronavirus disease 2019 (COVID-19) has emerged as a global pandemic, and the United States and European authorities established criteria for the release of COVID-19 patients from isolation in October 2020. However, a huge discrepancy exists between the hospital-discharge protocol for COVID-19 patients and the release of patients from in-hospital isolation. Our initially proposed criteria for in-hospital release from isolation was not adhered to by healthcare workers (HCWs) due to prevailing concerns regarding disease infectivity. Herein, we report difficulties encountered in attempting to establish a common understanding of the management of emerging infections. Methods: We performed a Google Form-based questionnaire survey targeting HCWs from Okayama University Hospital, Japan, via e-mail on January 21–28, 2021. The anonymous investigation required respondents to provide information regarding their background as well as perceptions regarding the requirement, level of understanding, and readiness for developing release criteria. Results: We obtained 150 eligible responses, including 57 (38.0%) from medical doctors and 53 (35.3%) from nurses. Most HCWs managing COVID-19 patients advocated for the implementation of the criteria, whereas those not working in that capacity did not (p<0.001). Over half of the HCWs indicated discomfort at seeing COVID-19 patients transitioning to general management even after meeting the criteria. Conclusions: It was challenging to establish a common understanding regarding the ideal criteria for in-hospital release of COVID-19 patients from isolation in our hospital. The dissemination of our experiences and multifaceted discussions with HCWs would be of great value as a countermeasure against the emergent pandemic. [ABSTRACT FROM AUTHOR]

Background: The coronavirus disease 2019 (COVID-19) pandemic is continuing unabated in Japan, as of October 2021. We aimed to compare first-year university students' psychological distress before the pandemic in 2019, during the pandemic in 2020, and one year after the onset of the pandemic, in 2021. Methods: The study conducted online surveys over three years from April to May each year. Participants were 400 first-year students in 2019, 766 in 2020, and 738 in 2021. We examined differences in scores on the Counseling Center Assessment of Psychological Symptoms—Japanese version (CCAPS-Japanese) between the three years using a one-way analysis of variance, and differences in the CCAPS-Japanese critical items using chi-squared test and residual analysis. Results: The average scores on the Depression and Generalized Anxiety subscale in 2021 were significantly higher than those in 2020, but remained the same as in 2019. The Academic Distress subscale score in 2020 was the worst compared to 2019 and 2021. Meanwhile, the number of students who experienced severe suicidal ideation increased year by year from 2019 to 2021. Conclusion: The mean mental health of first-year university students worsened after the onset of the COVID-19 pandemic, and recovered to the pre-pandemic level over the next two years. However, the number of high-risk students with suicidal ideation continued to increase. A system is required for early detection and support for students at high risk of mental health issues. [ABSTRACT FROM AUTHOR]

The coronavirus disease 2019 (COVID-19) pandemic has impacted the world economy in various ways. In particular, the drastic shift to telework has dramatically changed how people work. Whether the new style of working from home (WFH) will remain in our society highly depends on its effects on workers' productivity. However, to the best of our knowledge, the effects of WFH on productivity are still unclear. By leveraging unique surveys conducted at four manufacturing firms in Japan, we assess within-company productivity differences between those who work from home and those who do not, along with identifying possible factors of productivity changes due to WFH. Our main findings are as follows. First, after ruling out the time-invariant component of individual productivity and separate trends specific to employee attributes, we find that workers who worked from home experienced productivity declines more than those who did not. Second, our analysis shows that poor WFH setups and communication difficulties are the major reasons for productivity losses. Third, we find that the mental health of workers who work from home is better than that of workers who are unable to work from home. Our result suggests that if appropriate investments in upgrading WFH setups and facilitating communication can be made, WFH may improve productivity by improving employees' health and well-being. [ABSTRACT FROM AUTHOR]

Background: Prolonged periods of confined living on a cruise ship increase the risk for respiratory disease transmission. We describe the epidemiology and clinical characteristics of a SARS-CoV-2 outbreak in Australian passengers on the Diamond Princess cruise ship and provide recommendations to mitigate future cruise ship outbreaks. Methods: We conducted a retrospective cohort study of Australian passengers who travelled on the Diamond Princess from 20 January until 4 February 2020 and were either hospitalised, remained in Japan or repatriated. The main outcome measures included an epidemic curve, demographics, symptoms, clinical and radiological signs, risk factors and length of time to clear infection. Results: Among 223 Australian passengers, 56 were confirmed SARS-CoV-2 positive. Forty-nine cases had data available and of these over 70% had symptoms consistent with COVID-19. Of symptomatic cases, 17% showed signs and symptoms before the ship implemented quarantine and a further two-thirds had symptoms within one incubation period of quarantine commencing. Prior to ship-based quarantine, exposure to a close contact or cabin mate later confirmed SARS-CoV-2 positive was associated with a 3.78 fold (95% CI, 2.24–6.37) higher risk of COVID-19 acquisition compared to non-exposed passengers. Exposure to a positive cabin mate during the ship's quarantine carried a relative risk of 6.18 (95% CI, 1.96–19.46) of developing COVID-19. Persistently asymptomatic cases represented 29% of total cases. The median time to the first of two consecutive negative PCR-based SARS-CoV-2 assays was 13 days for asymptomatic cases and 19 days for symptomatic cases (p = 0.002). Conclusion: Ship based quarantine was effective at reducing transmission of SARS-CoV-2 amongst Australian passengers, but the risk of infection was higher if an individual shared a cabin or was a close contact of a confirmed case. Managing COVID-19 in cruise ship passengers is challenging and requires enhanced health measures and access to onshore quarantine and isolation facilities. [ABSTRACT FROM AUTHOR]

Due to COVID-19, many countries including Japan have implemented a suspension of economic activities for infection control. It has contributed to reduce the transmission of COVID-19 but caused severe economic losses. Today, several promising vaccines have been developed and are already being distributed in some countries. Therefore, we evaluated various vaccine and intensive countermeasure strategies with constraint of economic loss using SEIR model to obtain knowledge of how to balance economy with infection control in Japan. Our main results were that the vaccination strategy that prioritized younger generation was better in terms of deaths when a linear relationship between lockdown intensity and acceptable economic loss was assumed. On the other hand, when a non-linearity relationship was introduced, implying that the strong lockdown with small economic loss was possible, the old first strategies were best in the settings of small basic reproduction number. These results indicated a high potential of remote work when prioritizing vaccination for the old generation. When focusing on only the old first strategies as the Japanese government has decided to do, the strategy vaccinating the young next to the old was superior to the others when a non-linear relationship was assumed due to sufficient reduction of contact with small economic loss. [ABSTRACT FROM AUTHOR]

This study simulates the spread of the coronavirus disease (COVID-19) using a detailed agent-based model and the census data of Japan to provide a comprehensive analysis of the effects of contact-tracing apps. The model assumes two types of response to the app notification: the notified individuals quarantine themselves (type-Q response) or they get tested (type-T response). The results reveal some crucial characteristics of the apps. First, type-Q response is successful in achieving containment; however, type-T response has a limited curve-flattening effect. Second, type-Q response performs better than type-T response because it involves quarantine of those who are infected but have not become infectious yet, and the current testing technology cannot detect the virus in these individuals. Third, if the download rate of the apps is extremely high, type-Q response can achieve virus containment with a small number of quarantined people and thereby high efficiency. Finally, given a fixed download rate, increasing the number of tests per day enhances the effectiveness of the apps, although the degree of improved effectiveness is not proportional to the change in the number of tests. [ABSTRACT FROM AUTHOR]