Under-utilised Bluetooth tracing being killed off but, like Monty Python's parrot, might be just resting

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Like Monty Python's parrot, Bluetooth contact tracing might be just resting.

On the eve of phase 2, director general of health Ashley Bloomfield said the feature will be sunsetted. But an expert predicts it will make a comeback post-Omicron.

Meanwhile, new data underlines that the Ministry of Health barely made any use of the technology - which was designed by Apple and Google to automatically record close contacts with Covid suffers, then sent alerts.

Investigations by University of Auckland research fellow Andrew Chen indicated there was no technical issue. The Apple-Google solution did what it said on the tin.

It was more that, as Delta hit, overwhelmed contact tracing staff simply did not have the time to walk people through the process of uploading Bluetooth Tracing data from their phone to Ministry of Health servers, Chen told the Herald.

Information released under the Official Information Act to Herald stablemate BusinessDesk confirms Chen's work. It shows from February 25, 2021, to January 30, 2022, the Ministry of Health sent just 1317 close contact alerts to devices, based on Bluetooth data.

That's despite 2.4m of the 3.6m registered NZ Covid Tracer app users having enabled the feature.

Regardless, that resourcing issue is about to become academic.

Bloomfield told a Beehive briefing yesterday that the NZ Covid Tracer app feature was being sunsetted.

"We will use it into phase 2 until the numbers get quite high," Bloomfield said.

"It certainly has some utility but we would likely phase it out towards the end of phase 2," he said.

NZ will shift to Phase 2 at 11.59pm tonight (1000 new cases per day was the trigger for phase 2; phase 3 will kick in if and when NZ hits 5000 per day).

Chen advocated for more Bluetooth tracing earlier in the pandemic, but says Bluetooth alerts - and locations of interest, which will also be phased out - will no longer be appropriate.

"When we get phase 3, we'll be dealing with so many cases that we have to treat everyone as high-risk," Chen told the Herald this morning.

"We will need to drastically shift our approach. That means moving from looking for pockets of cases to just managing the impacts of the virus on our people."

In phase 3, the Ministry of Health will rollout tools to help people self-report their testing results and self-manage their contacts.

"We individually will have to take on some of the workload because it won't be possible to do it centrally if we have thousands or tens of thousands of new cases a day," Chen said.

"So we need to keep using the technology tools we have available to us to help avoid getting to phase 3 if we can - for now, keep scanning QR codes and keep Bluetooth Tracing on."

Auckland University research fellow Dr Andrew Chen. Photo / File

And Chen said even if Phase 3 is triggered and Bluetooth contact-tracing switched off, he expects the technology, and contact tracing to be brought back.

"We may be called to use these tools again when we get to the other side of Omicron with the tail end of the pandemic, when we return to stamping out pockets of cases. So this isn't goodbye forever, not quite yet."

How Bluetooth contact tracing works

Where manual QR code poster scanning creates a record of where you've, automated Bluetooth tracing keeps a log of who you've been in close contact with.

If you've been in close contact with an infected person (and the MoH has played its part, which hasn't happened much as per the main text above), you'll get an alert if you've been in close proximity to an infected person for several minutes. The alerts don't identify the person; they just let you know you were in the danger zone.

NZ's Bluetooth tracing system - which is built into the NZ Covid Tracer app - is based on the Google/Apple Exposure Notification Framework (often referred to as GAEN or ENF).

Image / Getty Creative

In approving Bluetooth tracing in 2020, then Privacy Commissioner John Edwards noted no personal information is shared with Apple or Google. And that your close-contact record is stored on your iPhone or Android in your pocket, rather than in the cloud, as an additional privacy safeguard. The information is only kept on your phone for 14 days. It can be shared with the Ministry of Health if you get diagnosed with Covid, but only if you give your permission.

Once Bluetooth tracing is enabled on your phone, it runs in the background.

Once it's enabled on your phone, you go about your life as usual.

As you wander around, your phone broadcasts an ID number (also known as a "key").

When your phone is physically close to another phone with Bluetooth Tracing enabled, for a set amount of time, the two phones exchange keys, and record them in a diary/log.

If one of the two phone owners tests positive for Covid-19, they are then asked by public health officials to (voluntarily) upload the keys on their device to a central Ministry of Health server.

Phones with Bluetooth Tracing enabled are checking that server on a regular basis and, if there are new keys, will download them and check them against their log. If there is a match, then the user is notified about the match, and prompted to isolate and get a test.

Importantly, MoH does not know the identity of people who have matched, so this system relies on people doing the right thing when notified.