In a recent report for CBBC Newsround I explained the theory behind how contact tracing apps work to reduce the spread of infectious diseases.

When this report went to air in May 2020, contact tracing apps were seen by many as a key tool in helping communities regain some of their social freedoms following restrictions to prevent the spread of coronavirus.

However, at the time of writing this – June 2020 – the UK’s contact tracing app still hasn’t been fully released, beyond a trial on the Isle of Wight.

And today the UK government revealed that its NHS contact tracing app will now change how it works, favouring “decentralised” technology supported by Apple and Google.

The initial version of the NHS contact tracing app was based on a centralised model recommended by scientists from Oxford University:

The team of Oxford scientists argue the UK’s choice of a centralised app architecture will significantly improve the NHS’s ability to refine, improve and evaluate the app’s configuration; they suggest it will ensure the app can rapidly and effectively guide the right people to self-isolate whilst enabling most people to start returning to normal life.

However, this change of direction appears to have been driven in part by mounting concerns over privacy and security – which might reduce the number of people comfortable using the app – along with technical challenges with how accurately the bespoke app was able to detect other smartphones.

Other countries have made similar u-turns, but all will hope that favouring a technology supported by Apple and Google will ensure better public trust and accuracy.

One thing is for sure: the idea that a contact tracing smartphone app might be a silver bullet to tame coronavirus has fallen very flat.