https://www.reuters.com/article/us-health-coronavirus-britain-tracing-ap/britains-covid-19-app-the-game-changer-that-wasnt-idUSKBN2400YM

As Britain's COVID-19 infections soared in the spring, the government reached for what it hoped could be a game changer – a smartphone app that could automate some of the work of human contact tracers.