The NHS Covid-19 App for England and Wales prevented up to 13,500 deaths

Written by scientists at The Alan Turing Institute and Oxford University, the analysis published in Nature covered the first three months of the App’s operation from late September to 31 December 2020. The full article can be downloaded here, and highlights include:

• The App was downloaded 21.6 million times in 2020, representing 56% of the eligible population aged – making it the second most downloaded Apple App Store free app last year. {It has now been downloaded over 26 million times}.
• It was used regularly by 16.5 million people (about 28% of the total population) and sent about 1.7 million exposure alerts advising people to isolate. 
• The authors estimate that for every percentage point increase in the app’s users, the number of Covid cases is reduced by up to 2.3%.
• The authors conclude that “these findings provide evidence for continued development and deployment of such apps in populations that are awaiting full protection from vaccines”.

The App was developed in under 12 weeks by Zühlke engineers working around the clock across 7 countries worldwide.  Creating this robust medical-grade app involved deploying new technologies and overcoming numerous technical and privacy-protection challenges.  These included:

• For maximum accuracy, its risk-scoring algorithm utilises the Google Apple Exposure Notification API Version 2 which enables better estimates of the distance between two phones based on Bluetooth signal strength.  It was the first contact tracing app worldwide to harness this technology.
• The logic for when and how long to place users into isolation after a positive exposure is very intricate, with over 500 possible scenarios depending on the individual circumstances. The team built a state machine to capture and handle this logic, overcoming the complexity of simple flowcharts.
• Other nations in the United Kingdom have their own COVID tracking apps. In order to protect users across borders, interoperability between this app and the others was a primary consideration. The team worked closely with their counterparts in the other countries to build and operate the system that allows the disparate apps to exchange keys and notify users of contacts from anywhere in the UK, Channel Islands, and Gibraltar.

Wolfgang Emmerich, CEO of Zühlke UK, who oversaw the project, said: “Everyone at Zühlke, especially the team who worked so hard to create this App, can be very proud of their role in saving so many lives”.