Digital contact tracing is becoming increasingly crucial in Japan, where the third wave of COVID-19 infections is overwhelming contact tracers at public health centers and testing their capacity to the limits.

Some of these facilities are now marshaling their contact-tracing workforce toward a tiny pool of patients deemed particularly high risk, leaving the vast majority of cases at the mercy of a state-developed tracing app known as the Contact-Confirming Application (COCOA).

One case in point is Kanagawa Prefecture, where — like in Tokyo — numbers of new cases spiked in January. Amid the surge, all of the prefecture's public health centers are currently encouraged to focus contact tracing almost exclusively on a demographic considered most prone to complications from the virus, including individuals in medical institutions and nursing homes. As such, Kanagawa in principle no longer manually investigates the contact history of most other patients, the rationale being that either their cohabitants or those alerted by COCOA will automatically be recognized as close contacts.