Coronavirus: Keep using NHS Covid app people urged

People should continue using the NHS Covid contact tracing app in England and Wales and isolate when asked to do so, Downing Street has said.

The prime minister's spokesman said the app had been an "important tool" and Boris Johnson continued to use it.

The software detects the distance between users and the length of time spent in close proximity - currently 2m or less and more than 15 minutes.

It comes amid a huge rise in alerts as infections surge.

The latest government figures show UK infections are continuing to rise, with 35,707 Covid cases reported on Friday - the highest daily cases figure since 22 January. A further 29 deaths within 28 days of a positive test were also recorded.

Earlier Transport Secretary Grant Shapps said the app's sensitivity may need to change when the 1m-plus rule ends on 19 July.

The system allows people who test positive to anonymously share their test result, triggering alerts for those detected as close contacts in the days before the test.

Under current rules, those who receive an alert are asked to stay at home for up to 10 days, although the Department of Health said the app "is, and always has been, advisory" - unlike the requirement to isolate if you are contacted directly by NHS Test and Trace.

Coronavirus restrictions are set to end on 19 July but the requirement to self-isolate if you have had both vaccine doses will only stop on 16 August, raising fears that millions of people would be asked to self-isolate this summer as people mixed more.

The hospitality industry and NHS trusts have warned MPs the knock-on effect for the economy and workplaces could be huge.

The prime minister's spokesman said: "A large number of the population continues to use the app and it has been an important tool in getting people to isolate and break the chain of transmission.

"It is important that people continue to isolate if they are asked to do so. We continue to ask people to isolate if they are asked to through the app."

The Welsh government has said people in Wales should continue to use the app even if social distancing rules differ from those in England. No date has been given for the end of the 1m-plus rule in Wales.

One possible solution could be to change the sensitivity of the app, so it would tell people to self-isolate only after closer and more prolonged contact.

But sources at the app developers told the BBC they have not yet been asked to do this, although they are planning a change from 16 August when people would be able to record that they were fully vaccinated to turn off the self-isolation countdown timer.

Mr Shapps told BBC Breakfast: "As our restrictions change, of course the app needs to change. Things like replacing the 1m-plus rule on 19 July might well lead to a review of the way the app itself needs to function."

The most recent figures for the last week of June show an extra 300,000 downloads, bringing the total to more than 26 million, but it is not known how many people are active users.

"It's in our interests as a society to carry on doing the things that protect each other," Mr Shapps said.

Technically, it wouldn't be very difficult to tweak the app to make it less "sensitive" - the hard bit is working out exactly what those tweaks should be.

Currently, two phones with the app installed, exchange a digital handshake, via bluetooth, every five minutes. It registers how far apart they are, and for how long.

If one of those phones then goes on to report a positive Covid test, other phones who were two metres away or less, for a duration of 15 minutes during a 24 hour period, are likely to receive an isolation alert.

As we have learned more about the virus, other factors have also been incorporated such as how infectious the person was likely to have been at the time the two phones were in close proximity.

Changing those parameters would be straightforward.

But fundamentally it's the volume of cases which are driving the volume of isolation alerts, not the app itself. In the last week of June there were 356,000 alerts, triggered by 61,000 positive test reports - that's about six app users isolating per Covid case.

When you look at it like that, it doesn't sound so excessive.

And because of the app's focus on privacy nobody, including the government, the police and the NHS knows who has been "pinged" - making it legally unenforceable.

Labour leader Sir Keir Starmer said he was concerned about the possible changes, saying weakening the app would undermine the track and trace system the government had spent billions on.

He said: "This feels like taking the batteries out of the smoke detector and that is never a good idea."

Dr Jenny Harries, the head of the new UK Health Security Agency, told MPs on Thursday she was "aware that people are choosing not to use the app" when asked about concerns people have been deleting it to avoid being "pinged".

Hinting at a change, she added there was "work ongoing at the moment because it is entirely possible to tune the app to ensure that it is appropriate to the risk".

A source close to Health Secretary Sajid Javid told the BBC "we are looking at the sensitivity of the app" and pointed out the sensitivity had been changed before - although they did not say what would change.

At present, if two phones running the app are close for long enough, and one of the two users later shares a positive coronavirus test via the app, then the other will receive an alert.

Users can also use the app to "check-in" to venues enabling it to notify them of any positive cases they may have encountered there -although the requirement to check-in will be lifted in England when lockdown rules ease further on 19 July.

A total of 496 venue alerts - which use the check-in data to alert people to potential contact with a positive case - were sent between 24 June and 30 June.

But alerts for people coming into close contact with someone testing positive soared by more than 60% in the last week of June to 360,000.

At the end of May, there were only 16,000 alerts in a week.

A BBC analysis has estimated 4.5 million people could be asked to self-isolate between this week and 16 August, as the number of infections continues to rise.

The NHS Covid-19 app is used in England and Wales. Wales, Scotland and Northern Ireland have their own powers to set coronavirus regulations and separate test-and-trace programmes.

Prof Sir Jonathan Montgomery, a healthcare law expert from University College London who advised the government on the initial launch of the app, said it could still be useful but the government needed to issue new guidance.

"The real reason we shouldn't abandon the tool is because so many transmissions of Covid happen before people realise they are unwell," he told Times Radio.