How effective are Coronavirus Contact Tracing Apps?

By now, it seems clear ‘social distancing’ is going to be a part of our lives for the foreseeable future. However, to get some parts of the economy moving again, and to reduce the sense of lockdown fatigue, public bodies across the globe are suggesting contact tracing apps may be the way forward – helping increase freedom, whilst balancing citizens’ safety.

In theory the methodology behind these apps stacks up. If this weren’t the case, huge amounts of time and resources from leading security companies would not be being spent. The apps will also be easy to use; we download them onto our phone, enable Bluetooth, we all record any COVID19 symptoms and we are sent an alert each time we pass someone in the street who later reported symptoms telling us we now need to self-isolate for 14 days.

However, there are so many variables involved, that the benefit of downloading one of these apps will unfortunately be very limited.

For one thing, only a very small percentage of people are likely to download the app. We’ve already seen this in Singapore with its ‘TraceTogether’ app. Despite the government’s public campaign to the country to download the app, only about one in six people in Singapore have actually done it.

In order for an app like this to work effectively, data modelers have said that effectiveness needs as many as 80% of smartphone owners in any country to install the app and adhere to its instructions. This take-up and adherence needs to run for many months. That percentage of downloads needed simply won’t happen. Based on what we’ve seen already in Singapore and Australia, a 30% install base is much more likely, and even this figure across a population would be a solid achievement for many countries.

When you combine this with the fact that a considerable number of people don’t know if they are a carrier for the virus, many more won’t rigorously report symptoms, and even fewer will get tested, the potential effectiveness of these apps suddenly looks rather limited.

Finally, of course, privacy implications will deter numerous people from downloading. Although decentralised apps have better privacy settings for users, with this model, public health bodies and governments cannot see where hotspots are breaking out and where stricter lockdown measures need to be put in place. Where this is the case, the onus to get tested and isolate really falls upon citizens as there is only very limited local data around, stored on devices and deleted after a specified time period.

On the other hand, a country using a centralised model uploads citizens’ data anonymously to a government server. With this comes the risk of hacking, and the ability of public bodies to know (even if not directly linked to your name) what peoples’ movements are like. It would be easy to see, for example, how many people are meeting in your area based on the number of Bluetooth encounters the phones have. That level of surveillance will make many uncomfortable, and yet, it may be the only way to really prevent the spread.

Overall, if phone-based contact-tracing is to be effective, governments worldwide will need to address low take-up rates, possibly by mandating use, and encourage citizens to continue using the app through the summer and into next winter, and making sure that those who receive alerts to isolate or seek testing do so whenever instructed. In major cities this will be near impossible.

Singapore already seems to have realised this and has instead now turned to a different method of tracing. SafeEntry, checks-in citizens using their formal ID or a QR code on their smartphone in busy locations. Businesses failing to check-in visitors or customers risk penalties and deployment is mandatory. It will be interesting to see if this is a sign of contract tracing to come.

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