Why contact tracing technology has been slow to make an impact. Ed Butler speaks to Jenny Wanger from the Linux Foundation Public Health in the US where many states are only now rolling out contact tracing apps, months after many countries around the world. We hear from Colm Harte, technical director at NearForm, the company behind Ireland's app, which has been downloaded by about a quarter of the population. Chan Cheow Hoe, the chief digital technology officer for the Singapore government, talks about the success of digital contact tracing in his country. And the BBC's technology correspondent Rory Cellan-Jones explains why contact tracing apps are no longer being seen as the silver bullet in the fight against Covid-19.

(Photo: The National Health Service contact tracing app rolled out in England and Wales. Credit: Getty Images)