Effectiveness of the COVID-19 Contact-Confirming Application Incorporating Secondary Indirect Contact Notification Function on Decreasing the Number of Infectors

Abstract

To decrease the number of COVID-19 infectors, Ministry of Health, Labour and Welfare developed and released the COVID-19 contact-confirming application (COCOA) on 19th June 2020. Users of the application can know whether they contacted infectors who are/were positive of COVID-19 or not. If the contacted persons stay indoors, the number of new infectors can be decreasing. However, as of October 2020, the number of infectors of COVID-19 is increasing in Japan. Therefore, the additional function to decrease the number of infectors is necessary. In this paper, the function of the secondary indirect contact notification is proposed. In other words, the application informs whether they contacted infectors or not to not only the primary direct contact persons but also the secondary indirect contact persons. To verify the effectiveness of the additional function on decreasing infectors, we develop a simulator incorporating it. Herein, we report the simulator and effectiveness of the secondary indirect contact notification on decreasing infectors.