UK Health Secretary Matt Hancock has insisted the country’s new coronavirus tracing app will be effective despite fears the vast majority of the population won’t download it.
The rollout of the NHS Test and Trace app follows months of delay and questions about its effectiveness in the face of mixed results from other countries which have already deployed such apps.
As the software is voluntary, its success depends heavily on how many people choose to download and use it.
International examples of similar apps show a take-up rate of about 10% to 30% - well short of the National Health Service target of 80%.
But the app is being hailed as an “important step forward” in the fight against the “invisible killer”.
Speaking on BBC’s Radio 4 programme, Mr Hancock said: “People have been asking me, Is there a number that you need? Is there a proportion of the population that you need for this to work?’
“The truth is the more people who get it, the safer we will all be.
“It’s dead simple to download.”
When two devices running the app are close to each other, they exchange Bluetooth "handshakes" to determine the distance and duration, measured in sessions lasting five minutes.
If the points threshold is met and one of the two owners later shares a positive coronavirus test via the app, then the other will receive an alert.
A QR code scanning feature is available, allowing people to check-in to venues they visit and easily share their contact details for human tracing efforts.
Some 160,000 businesses have already downloaded QR codes for use in their facilities.
The app was initially trialled on the Isle of Wight and the London borough of Newham but the pilot programme was plagued with difficulties after residents complained the app did not work.
The government then abandoned plans to build the app itself and instead relied on software provided by Google and Apple.
The health secretary was also asked about the risk that some people would be told to self-isolate based on a “false positive”.
There is a risk the app could mistakenly think a user is within two metres of an infectious person due to malfunctioning Bluetooth signals, which can be affected by surrounding objects.
Speaking on Sky News, Mr Hancock denied that would be the case for the vast majority of users.
He said: “The proportion of people for whom it gives a positive is very, very small.”
He added: “We have worked extensively with tech companies, international partners, and privacy and medical experts – and learned from the trials – to develop an app that is secure, simple to use and will help keep our country safe.
“Today’s launch marks an important step forward in our fight against this invisible killer and I urge everyone who can to download and use the app to protect themselves and their loved ones.”
The UK’s major network operators, including Vodafone, Three, EE and O2, giffgaff, Tesco Mobile, Sky Mobile and Virgin Mobile have agreed to “zero-rate” data charges incurred by all in-app activity, meaning they will not be charged for using it.
