NTT Docomo and Apple mobility data compared as countermeasures against COVID-19 outbreak in Japan

Background In Japan, as a measure to inhibit the COVID-19 outbreak, voluntary restrictions against going out (VRG) have been applied. Object Mobility information provided by Apple Inc. and NTT Docomo were assessed in terms of its usefulness in predicting conditions exacerbating an outbreak. Method A polynomial function was applied to daily Apple and Docomo data to calculate the observed R(t). Results The correlation coefficient among Apple and Docomo data was 0.91. The adjusted coefficient of determination for R(t) for the whole study period was higher using Docomo data than when Apple data were used. When we regressed R(t) on daily Apple and Docomo data simultaneously, the estimated coefficient of Docomo data was not significant. Discussion and Conclusion We demonstrated that Apple mobility data might be superior to Docomo data for explaining the entire course of the COVID-19 outbreak in Japan.