The research suggests the app stopped between 200,000 and 900,000 infections between 1st October and 31st December 2020, when 1.9 million people were infected with coronavirus in England and Wales.
Christophe Fraser, Professor of Pathogen Dynamics at Oxford University’s Big Data Institute, Nuffield Department of Medicine, explains: 'We used two separate approaches to analyse the impact of the more than 1.5 million notifications sent by the app in 2020, and both showed that between 200,000 and 900,000 infections have been averted. The impact of the app could be increased if more people use it. For each 1% increase in users we estimate the number of cases will drop by between 0.8% and 2.3%.'
The report shows the app was downloaded onto over 21 million phones, out of 33.7 million eligible people with compatible smartphones living in England and Wales. In 2020, the app sent out an average of 4.4 quarantine notifications for each user who shared their positive test result though the app. Most alerts went out in the second half of December when cases were rising rapidly across the UK due to the new B117 variant.
The story is also featured in the Fraser Group Coronavirus blog.