To accommodate this, the ‘risk threshold’ was due to be lowered, but this change did not take place at that time. The updated version of the app addresses this by lowering the threshold at which users are deemed to be at risk of having caught the virus and alerted to self-isolate. The threshold was due to move from 900 to 180, but because we have a new statistical algorithm taking advantage of improved distance estimation, we are now lowering it to 120.
The update to the risk threshold is expected to increase the number of people asked to self-isolate by the app, having been in close contact with someone who has tested positive. We believe lowering the threshold is necessary to reduce the R rate and break the chain of transmission.