JMIR Publications

ABSTRACT

Background:

In Japan, as a countermeasure against the COVID-19 outbreak, voluntary restrictions against going out (VRG) from a residence were announced from the end of March by national and local governments in preference to lockdowns like those instituted in European and North American countries.

Objective:

We examined some associations among going out information provided by Apple Inc. and estimated an effective reproduction number R(t).

Methods:

We regressed R(t) on a polynomial function of daily Apple Inc. data. From estimation using the whole period, the sub-periods delimited by March 10 were analyzed.

Results:

Estimation results indicate R(t) as 1.72 if VRG ceases and mobility reverts to a normal level. However, the critical level of R(t)<1 was achieved at a 89.3% of the normal level of mobility.

Conclusions:

Results indicate that a 10% reduction from the normal number of trips will be necessary until herd immunity is achieved. Complete cessation of VRG might not be necessary to avoid re-emergence of the outbreak.