NHS app pinging some phones, not others

Reports of inconsistencies with technology as only some people who were in same place told to isolate

THE NHS Covid app is “pinging” some phones and not others despite them being exposed to the virus in the same location at the same time.

The Sunday Telegraph found that only one of two Apple iPhones received a self-isolation warning after both were carried together for almost a week and taken to a number of indoor venues.

The findings have prompted a former government adviser for the app to call on ministers to make the self-isolation notifications less stringent for people who have had both vaccine shots.

The investigation comes as the NHS Covid app pinged a record number of people last week, with 530,126 being advised to self-isolate for up to 10 days.

The mass alerts caused chaos for businesses and public services as staff called in sick en masse.

A number of users have also reported inconsistencies with the technology as people pinged after trips to restaurants or pubs found that those they dined with had not received alerts.

Last week The Telegraph checked into a number of restaurants between Monday and Thursday with two phones, an iPhone 7 and an iPhone 6S, after setting up the NHS app on both.

On Friday afternoon at 1pm, the iPhone 7 was pinged with instructions to self-isolate until midnight next Sunday, July 25. However, no alert was triggered on the iPhone 6S.

The app works by using phones’ bluetooth radio signals – originally designed to connect devices such as wireless headphones – to detect when other phones with the app are nearby.

It then anonymously logs phones that have been within two metres for around 15 minutes and triggers an alert if the owner of any logged phone registers a positive Covid test.

Jon Crowcroft, a professor of computer science at Cambridge University who developed the UK’s first contacttracing app in 2009 in response to swine flu, said bluetooth was not designed for tracking people’s proximity.

He said it had been repurposed for contact tracing to use a number of signals, from bouncing bluetooth off nearby phones, to “estimate” how close other people are and for how long.

But he said that while the UK app was very accurate compared with other countries’ versions, the signal could be affected by factors such as whether one person had their phone on a table while another had it in a bag, which would dull its ability to detect other devices.

Prof Crowcroft said that bluetooth also had varying effectiveness in different models of smartphone, but that tech giants such as Apple and Google had worked to standardise how their handsets reacted to the UK app.

The Cambridge professor, who advised the Government on the development of the NHS Covid app, urged ministers to change its self-isolation advice from a one-size-fits-all approach to recognising that vaccinated people are at less risk of contracting and spreading the virus.

“I would change the advice to the public in the text [of the notification],” Prof Crowcroft said. “If the app knows that you have marked yourself as double-dosed, it could say you don’t have to isolate or give less strong advice.”

contacted the Department of Health for a response.