Why You Should Keep Your Contact Tracing App


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QR code scanning may have been discontinued by the government, but that doesn’t mean it’s no longer useful. explains Andrew Chen.

The Prime Minister has announced that scanning QR codes and displaying QR codes by businesses is no longer required. Prior to this announcement, we were seeing a significant drop in QR code scans as we entered the Omicron wave, with manual contact tracing reduced in phase 3 of the wave. With places of interest no longer published, and therefore no location-based exposure notifications via NZ COVID Tracer, the downward trend was to be expected.

But there are two reasons to keep the app: to keep your own records and Bluetooth tracking.

The fall of QR codes

Our research identified many factors that influence the decision to participate in digital contact tracing, ranging from availability of smartphones to trust in technology to privacy concerns. But two of the most important factors are changes in the perception of risk and the perception of efficacy. Throughout the pandemic, we have seen QR code scans increase each time there were new community cases – a response to perceived risk suddenly increasing – then slowly decreasing over time. The steeper declines more recently can be attributed to a decrease in perceived efficiency (as well as a general decline in mobility as more and more people work from home).

Thus, one of the core functions of NZ COVID Tracer – scanning QR codes and generating location-based exposure notifications – has fallen into disuse. Does this mean that the whole application is now useless? No, because this is not the only function of the application.

Scanning QR codes and keeping track of where you’ve been is always useful if you catch Covid-19 and need to remember who to tell. It may not be easy to remember who you saw on which days of your infection period. Using this tool is, of course, a personal choice, as there is no longer a central contact-tracing device to notify people while keeping your identity anonymous.

It’s disappointing that displaying a QR code is no longer mandatory for businesses, as it reduces the ability to collect this information – a major supermarket chain has already ordered stores to remove the codes. Rebuilding infrastructure takes time and if, as the Prime Minister noted, a new variant requires us to scan again, we will not be able to react as quickly as if we had simply left the QR codes in place.

The rise of Bluetooth tracking

The use of Bluetooth tracking has become much more prominent over the past month. The daily tally of more than 2.3 million devices participating in the system equates to nearly 60% of the adult population – one of the highest participation rates in the world for a Bluetooth-based digital contact tracing tool .

After reporting early in the Delta outbreak that Bluetooth tracing was not being used at all, contact tracers began using the tool in limited volumes. It was only when human phone calls were replaced with an online self-report form that Bluetooth tracing codes were consistently provided to a higher proportion of cases, leading to a large increase in uptake. Over the past week, we’ve seen thousands of cases provide data and tens of thousands of people issued exposure notifications.

As a reminder of how the system works (skip two paragraphs if you already know this), when Bluetooth tracing is enabled with NZ COVID Tracer installed, your phone will emit randomly generated codes. Other phones listen to these codes and record which ones they hear and how well they hear them (based on “signal strength”). If you then test positive for Covid-19, you are asked to complete a self-reported contact tracing form for the Department of Health, detailing where you have been and when you were symptomatic. Additionally, you are voluntarily given codes to enter into the NZ COVID Tracer app, which authorizes the app to upload your location log and BT codes to the Department of Health.

Other people’s phones periodically check Department of Health servers for the Bluetooth codes of people who have been infected with Covid and check for matches against codes they’ve heard, locally on the device. If a match occurs, an exposure notification is generated to alert the user, and no information other than an analysis ping (a message that a notification has been generated) is sent to the Department of Health , maintaining anonymity. Bluetooth tracking doesn’t record where you are, and contacts are matched based on proximity rather than location. While there are scenarios where location-based contact tracing is more useful, the advantage of Bluetooth is that it works passively in the background – once you turn it on, it works and users don’t. have nothing else to do to keep it. Go.

This system is currently telling thousands of people every day that they may have been in contact with someone who has Covid. This means that these people are better informed to assess the risks on a day-to-day basis. Maybe I should work from home and move some meetings online. Maybe it’s safer for me not to go to that birthday party tonight. Maybe this sore throat is more than just talking too much and I should do a RAT. The exposure notification indicates that a person may have been exposed to Covid, rather than assessing the risk based on the general mood.

Of course, the system is not perfect. Less than 10% of daily cases upload their Bluetooth tracing data voluntarily, although this may increase as the Department of Health has adjusted the self-report form to provide NZ COVID Tracer upload codes earlier in the process. There will be many people who have been exposed but are completely missed by the system. Bluetooth signals are heavily impacted by the environment, reducing system accuracy. The system doesn’t know if you were wearing a mask or were in a well-ventilated area when you were near an infected person, so there will be false positives. The system also still operates on contact thresholds better suited to the Delta variant rather than the even more infectious Omicron. These are all weaknesses of this system that we should recognize.

Keep the app

But in a landscape where we are increasingly taking care of our own safety and mitigating our own risk, many of us want more information rather than less to improve our decision-making. The Bluetooth system adds some value, which is probably better than nothing. Fears of the ‘pingdemic’ as seen overseas have not materialized here, which might lead us to wonder why this tool hasn’t been used more widely, sooner. Maybe if we had used it more in earlier phases, there would be more awareness and trust around the tool now.

The upshot of all this is that if you have Bluetooth tracing enabled with NZ COVID Tracer installed on your phone, don’t uninstall the app just because you no longer scan QR codes. If you delete the application, the system will no longer work and you will not receive notifications. Of course, participation in Bluetooth tracking is voluntary, but its effectiveness relies on a high proportion of the population using it. And if you get sick with Covid and are asked to complete the contact tracing form, consider getting NZ COVID Tracer download codes and providing your Bluetooth tracing data – it’s one of the last ways reduce the spread of the virus and help keep people around you safe.