The NHS COVID-19 app is no longer in use and the Isle of Wight trial has now ended. This is archived information from 18 June 2020. If you still have the app, please uninstall it.
The ‘contact risk model’ that is used to identify when app users are alerted considers distance between contacts based on Bluetooth signal strength. Bluetooth signal strength is reduced through walls and therefore less likely to satisfy the necessary contact criteria.
It is also important to note that notification alerts are based over multiple days of contact and not necessarily based on a single individual contact.
NHS doctors and scientists are continuously updating this model to make it as accurate as possible.