Coronavirus: Isle of Wight contact-tracing app trial - a mixed verdict so far

It is 10 days since all Isle of Wight residents were invited to test the NHS app at the heart of the government's test, track and trace strategy. So how's it going?

Mixed would probably be a fair verdict.

The big concern was how many people would download it. Epidemiologists suggest that for the UK as a whole, about 60% of the population needs to install and use the software for it to live up to its full potential.

So when Downing Street says there have been roughly 60,000 downloads, that's not a bad result. The island's population is 140,000, and its inhabitants are slightly older and less likely to own a smartphone than the UK average.

But one cautionary note - that 60,000 may include some who downloaded it twice or are from the mainland.

Still that compares well with other experiments. About 20% of the population of Singapore downloaded its contact-tracing app, and last week an Australian government app had been installed by roughly a quarter of its population.

But here's the key question - does it work? Are users being alerted to take action after coming into contact with the virus?

Here, there is very little to go on. What we know is that there are just 173 confirmed cases of Covid-19 on the Isle of Wight. With most people still in lockdown, it is quite unlikely that any single individual using the app would have come into contact with an infected person.

Then there is the fact that what's been offered is an early, unsophisticated version of the app.

At this stage, it only asks someone who feels unwell about two symptoms - a high temperature and a continuous cough.

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Depending on their answers, they may then be directed to a call centre to order a medical test.

People with whom they recently came into proximity may be sent alerts, warning them they need to be "super careful", as one of the app team put it to me, and be on the lookout for their own symptoms.