State of emergency and human mobility during the COVID-19 pandemic in Japan

Introduction: The Japanese government declared a state of emergency (SoE) to control the spread of the coronavirus disease (COVID-19). However, the requirements of these SoE were less stringent than those in other nations. It has not been assessed whether soft containment policies were sufficiently effective in the promotion of social distancing or the reduction of human contact. Methods: Mobility changes across different travel destinations, such as, (a) retail and recreation spaces; (b) supermarkets and pharmacies; (c) parks; (d) public transportation; (e) workplaces; and (f) residential areas, were analysed using the Google mobility index to assess social distancing behaviour in all Japanese prefectures between 15 February 2020 and 21 September 2021. The changes were evaluated through the utilisation of an interrupted time-series analysis after adjustment for seasonality and various prefecture-specific fixed-effects, and distinguishment of potential heterogeneity across multiple SoEs and the time that had passed after the declaration. Results: The mobility index for retail and recreation exhibited an immediate decline of 7.94 percent-points (95%CI: -8.77 to -7.12) after the declaration of the SoE, and a further decline after the initial period (beta: -1.27 95%CI: -1.43 to -1.11). However, it gradually increased by 0.03 percent-points (95%CI: 0.02-0.03). This trend was similar for mobility in other places. Among the four SoEs, the overall decline in human mobility outside the home was the least significant in the third and fourth SoE, which suggests that people were less compliant with social distancing measures during these periods. Conclusions: Although government responses to the pandemic may aid the controlling of human mobility outside the home, their effectiveness may decrease if these interventions are repeated and enforced for extended periods. A combination of these with other measures (i.e. riskcommunication strategies) would enable even mild containment and closure policies to effectively curb the spread of the virus.