By Doug Faulkner & Joseph Lee
People should proceed utilizing the NHS Covid interaction tracing app successful England and Wales and isolate erstwhile asked to bash so, Downing Street has said.
The premier minister's spokesperson said the app had been an "important tool" and Boris Johnson continued to usage it.
The bundle detects the region betwixt users and the magnitude of clip spent successful adjacent proximity - presently 2m oregon little and much than 15 minutes.
It comes amid a immense emergence successful alerts arsenic infections surge.
The latest authorities figures amusement UK infections are continuing to rise, with 35,707 Covid cases reported connected Friday - the highest regular cases fig since 22 January. A further 29 deaths wrong 28 days of a affirmative trial were besides recorded.
Earlier Transport Secretary Grant Shapps said the app's sensitivity whitethorn request to change erstwhile the 1m-plus regularisation ends connected 19 July.
The strategy allows radical who trial affirmative to anonymously stock their trial result, triggering alerts for those detected arsenic adjacent contacts successful the days earlier the test.
Under existent rules, those who person an alert are asked to enactment astatine location for up to 10 days, though the Department of Health said the app "is, and ever has been, advisory" - dissimilar the request to isolate if you are contacted straight by NHS Test and Trace.
The hospitality manufacture and NHS trusts person warned MPs the knock-on effect for the system and workplaces could beryllium huge.
The premier minister's spokesperson said: "A ample fig of the colonisation continues to usage the app and it has been an important instrumentality successful getting radical to isolate and interruption the concatenation of transmission.
"It is important that radical proceed to isolate if they are asked to bash so. We proceed to inquire radical to isolate if they are asked to done the app."
One imaginable solution could beryllium to alteration the sensitivity of the app, truthful it would archer radical to self-isolate lone aft person and much prolonged contact.
But sources astatine the app developers told the BBC they person not yet been asked to bash this, though they are readying a alteration from 16 August erstwhile radical would beryllium capable to grounds that they were afloat vaccinated to crook disconnected the self-isolation countdown timer.
Mr Shapps told BBC Breakfast: "As our restrictions change, of people the app needs to change. Things similar replacing the 1m-plus regularisation connected 19 July mightiness good pb to a reappraisal of the mode the app itself needs to function."
The astir caller figures for the past week of June amusement an other 300,000 downloads, bringing the full to much than 26 million, but it is not known however galore radical are progressive users.
"It's successful our interests arsenic a nine to transportation connected doing the things that support each other," Mr Shapps said.
Technically, it wouldn't beryllium precise hard to tweak the app to marque it little "sensitive" - the hard spot is moving retired precisely what those tweaks should be.
Currently, 2 phones with the app installed, speech a integer handshake, via bluetooth, each 5 minutes. It registers however acold isolated they are, and for however long.
If 1 of those phones past goes connected to study a affirmative Covid test, different phones who were 2 metres distant oregon less, for a duration of 15 minutes during a 24 hr period, are apt to person an isolation alert.
As we person learned much astir the virus, different factors person besides been incorporated specified arsenic however infectious the idiosyncratic was apt to person been astatine the clip the 2 phones were successful adjacent proximity.
Changing those parameters would beryllium straightforward.
But fundamentally it's the measurement of cases which are driving the measurement of isolation alerts, not the app itself. In the past week of June determination were 356,000 alerts, triggered by 61,000 affirmative trial reports - that's astir six app users isolating per Covid case.
When you look astatine it similar that, it doesn't dependable truthful excessive.
And due to the fact that of the app's absorption connected privateness nobody, including the government, the constabulary and the NHS knows who has been "pinged" - making it legally unenforceable.
Labour person Sir Keir Starmer said helium was acrophobic astir the imaginable changes, saying weakening the app would undermine the way and hint strategy the authorities had spent billions on.
He said: "This feels similar taking the batteries retired of the fume detector and that is ne'er a bully idea."
Dr Jenny Harries, the caput of the caller UK Health Security Agency, told MPs connected Thursday she was "aware that radical are choosing not to usage the app" erstwhile asked astir concerns radical person been deleting it to debar being "pinged".
Hinting astatine a change, she added determination was "work ongoing astatine the infinitesimal due to the fact that it is wholly imaginable to tune the app to guarantee that it is due to the risk".
A root adjacent to Health Secretary Sajid Javid told the BBC "we are looking astatine the sensitivity of the app" and pointed retired the sensitivity had been changed earlier - though they did not accidental what would change.
At present, if 2 phones moving the app are adjacent for agelong enough, and 1 of the 2 users aboriginal shares a affirmative coronavirus trial via the app, past the different volition person an alert.
Users tin besides usage the app to "check-in" to venues enabling it to notify them of immoderate affirmative cases they whitethorn person encountered determination -although the request to check-in volition beryllium lifted successful England erstwhile lockdown rules easiness further connected 19 July.
A full of 496 venue alerts - which usage the check-in information to alert radical to imaginable interaction with a affirmative lawsuit - were sent betwixt 24 June and 30 June.
But alerts for radical coming into adjacent interaction with idiosyncratic investigating affirmative soared by much than 60% successful the past week of June to 360,000.
At the extremity of May, determination were lone 16,000 alerts successful a week.
A BBC investigation has estimated 4.5 cardinal radical could beryllium asked to self-isolate betwixt this week and 16 August, arsenic the fig of infections continues to rise.
The NHS Covid-19 app is utilized successful England and Wales. Wales, Scotland and Northern Ireland person their ain powers to acceptable coronavirus regulations and separate test-and-trace programmes.
Prof Sir Jonathan Montgomery, a healthcare instrumentality adept from University College London who advised the authorities connected the archetypal motorboat of the app, said it could inactive beryllium utile but the authorities needed to contented caller guidance.
"The existent crushed we shouldn't wantonness the instrumentality is due to the fact that truthful galore transmissions of Covid hap earlier radical realise they are unwell," helium told Times Radio.