The limitations of Bluetooth for contact tracing apps

Available for over a year

Bluetooth is the key technology behind numerous coronavirus contact tracing apps around the world, but Professors Stephen Farrell and Douglas Leith of Trinity College, Dublin are questioning its effectiveness. Apps use proximity measurements to judge whether you could have been infected. Rory Cellan-Jones asked Professor Stephen Farrell what he's found. (Image: Contact tracing app on mobile phone Credit: Getty Images)