A problem in the design of the NHS Covid-19 app means people could be told to self-isolate unnecessarily.
The app includes the option to scan QR codes at venues such as restaurants, shops and places of worship. If someone then tests positive after visiting that place, those who also scanned the QR code will be told they may be at risk and given advice.
But the app does not let those people check out of the location again. That means they may be told to self-isolate on the basis of having checked in at a hotspot location — despite having left long before the person who tested positive arrived.
The app does not have access to a users’ location information, and so the only way that it knows if a person was at a specific location is if they scan the venue’s QR code when they arrive.
Information in an FAQ on the app’s support pages makes clear that this decision is part of the design of the app, and that human contact-tracers will follow up and may then instruct you that the warnings about being potentially at risk could be wrong.
“The app registers what time you enter a venue but does not register what time you leave,” it reads.
"If people with coronavirus (COVID-19) were at the venue at a similar time as you, a human contact tracer from the Contact Tracing and Advisory Service (CTAS), or the Joint Biosecurity Centre (JBC), will look into the case. They'll evaluate the risk level based on the type of venue and the details of the case. This will help them decide who may be at risk.
“You do not need to check out of a venue. Your phone will register when you check into somewhere new, and it will automatically check you out of your last venue at midnight.”
At the moment, self-isolation from the app is voluntary, unlike instructions from human contact tracers. People can be fined up to £10,000 if they ignore instructions from those contact-tracers that they need to self-isolate.