Even Boris Johnson, the Prime Minister, and Rishi Sunak, the Chancellor, were not immune. They were pinged after fellow Cabinet minister Sajid Javid, the Health Secretary, tested positive.
And yet the app is actually used relatively little in the UK, with only 25 million downloads out of a population of nearly 70 million.
Although test and trace can be an effective tool to contain the spread of a virus, it’s also becoming increasingly controversial and hard to enforce.
So how are other countries dealing with it?
After a bumpy start, the French tracing app, TousAntiCovid, has been downloaded by around 20 million people out of nearly 70 million, but only about half that amount actively use it.
If you are pinged, you are advised to get tested, but this is not compulsory. Around 200,000 people in total have so far been informed of close contact with an infected person.
Most tracing is instead done manually by French health agencies who message contacts of someone who tests positive via text message. Again, nobody checks up on whether people actually self-isolate.
Uptake of the official Italian tracing app, Immuni, has been low. Out of a population of 60 million, the app has been downloaded by just 11.6 million people.
Since it went into operation last year, just 100,000 notifications have been sent and 19,600 people were found to be positive to the virus.
If you are ‘pinged’, there is no requirement to self-isolate, but you are told to contact your local doctor for further advice.
If someone tests positive on Belgium’s app, Coronalert, they must manually input the names and details of people they have come into contact with – there are no automatic ‘pings’.
Those who are contacted are expected to complete a 10-day self-isolation and take two free PCR tests.
As of last week, 2.8 million of Belgium’s 11.5 million population had downloaded the app.
While just over 80,000 people registered positive test results on the app, only 36 per cent of them shared details of close contacts.
There is no national contact-tracing program in the United States, and local attempts to promote and enforce schemes have largely failed.
Contact tracers can recommend that infected people self-isolate, but they have no power to enforce that. In Seattle, tracers found 80 percent of the people they reached were not in quarantine, even if they had symptoms.
Many calls are ignored entirely – last summer in Maryland, 25 per cent of people called by contact tracers didn’t pick up.
State health authorities have introduced their own apps, but the pickup has been poor and there are obvious flaws, such as when people cross state borders.
In China, nobody is exempt from contact tracing. Being ‘pinged’ means being tested and at least a 14 to 21-day quarantine that is strictly enforced.
Both central and local governments have developed mobile apps that track individuals, primarily via phone pings to telecom towers.
The app is required in order to enter public places, such as the tube, parks, malls and restaurants and is tied to your mobile number and Chinese ID or passport, so there’s no way to cheat the system. Anyone who does risks jail time.
Having recently travelled to an area with cases – even if they started after you left – also means being ‘pinged’.
India’s app, Aarogya Setu (“bridge to health”), has been downloaded a whopping 100 million times, but that’s still a fraction of the country’s total population of 1.38 billion.
Despite threats of being barred from hospitality venues, fines or even arrests for not having the app, many Indians avoided it because it was impractical or due to privacy concerns. It has been largely defunct since last summer.
Contact tracing was instead left to state governments, but very few had the resources to do so properly – a major factor in the explosion of infections earlier this year.
Taiwan relies heavily on contact-tracing teams who use human intelligence, mobile phone signals and a QR code system to track down contacts of infected people.
It is compulsory to scan a QR code whenever you enter a public building. This allows the Centres for Disease Control to reach you if you’ve been close to a confirmed case and need to self-isolate.
There’s also a voluntary app that will tell you if you come within 2 metres of an infected person for at least two minutes. You are then urged to contact the health authorities.