The Department of Health and Social Care has said that more than 1.7 million users have been asked to isolate as a result of a close contact since the launch of the NHS COVID-19 app, helping to break chains of transmission.

The app, launched in September, is the fastest way to notify the public they have been at risk of contracting the virus, sending alerts to close contacts to tell them to isolate as quickly as 15 minutes after an app user enters a positive result into the app.

It has been downloaded 21.63 million times, representing 56 per cent of the eligible population aged over 16 with a smartphone, making it the the second most downloaded free iPhone app on the Apple App Store in 2020.

Research conducted by scientists at The Alan Turing Institute and Oxford University shows for every one per cent increase in app users, the number of coronavirus cases in the population can be reduced by 2.3 per cent.

Health Secretary Matt Hancock said: “The NHS COVID-19 app is an important tool in our pandemic response. We know it has instructed hundreds of thousands of at-risk people to self-isolate since it launched in September – including me – and this analysis shows it has been hugely effective at breaking chains of transmission, preventing an estimated 600,000 cases.

“Isolating and knowing when you have been at risk of catching coronavirus is essential to stopping the spread of this virus, and the app is the quickest way to notify you if you are at risk. I want to thank all those who have played their part by downloading and using the app, and urge those who haven’t to take the simple step to protect your communities and loved ones and download it.”