Covid 19 Delta outbreak – Revealed: How contact-tracing capacity has been nearly doubled for summer outbreaks

Contact-tracing capacity has not only nearly doubled to help ring-fence outbreaks over summer, but Ayesha Verrall warns it won’t help much if engagement with the marginalised isn’t improved.

The Associate Health Minister says the new standing capacity is for 3550 contact calls a day, with surge capacity for 11,000 a day.

This is almost twice the previous surge capacity for 6000 contacts from 1000 cases a day, though this was widely viewed as fanciful after the system came under pressure from daily case numbers that were nowhere near 1000.

Verrall told the Herald that how the system will be deployed will lead to real improvements.

“We have a small group of unvaccinated people who will be over-represented among cases, but the health system might have challenges engaging with them. That might be from being from underserved communities, or mistrust of authority, or past bad experiences in the system.”

Such challenges saw the virus continue to spread in Auckland at a time when it looked like it was close to being stamped out.

“The system needs to be more responsive to different needs – that’s the lesson of the August outbreak … People from the margins deserve to be looked after,” Verrall said.

She is also defending the preparation before Delta leaked into the community in August, saying the poor performance of the contact-tracing system was more about people’s reluctance to share information rather than capacity issues.

Contact-tracing will play a critical role in the Covid response over summer alongside testing, vaccination coverage, and the public health measures in the traffic light system.

The system came under intense stress in the first two weeks of the outbreak, with people in testing station queues for hours, and only about 60 per cent of contacts isolating within 48 hours of a positive case being notified.

The performance benchmark is at least 80 per cent, the same as for isolating contacts within 24 hours of the contact being identified. This also failed to reach the benchmark in those first two weeks, though it was only just below par.

Both these indicators reached the benchmark by week three, when case numbers were falling, but fell below 80 per cent from mid-October, when case numbers again reached 75 a day.

The ministry’s standing capacity at the time was meant to be able to contact-trace for 180 cases a day, with surge capacity for 1000 cases a day – numbers that the Delta outbreak never came close to.

But Verrall said the issue was getting cases to co-operate with public health officials.

“I don’t believe the capacity and throughput have been the problems,” she told the Herald.

“The types of things that were making those indicators slip were things like a case being very difficult, and having to take quite a lot of time to build sufficient trust to be able to identify the contacts and contact them.”

That was evident in mid-October, after the virus seeded among marginalised groups – including gangs, the homeless, and people with mental health or addiction issues – but it was also an issue with the Assembly of God church cluster early in the outbreak due to overstayer concerns.

From 6000 to 11,000 contacts a day

Verrall is the infectious diseases expert who, prior to becoming an MP, recommended to the Ministry of Health last year for contact-tracing capacity for 1000 new cases a day.

That benchmark was eventually agreed to by the ministry, following several independent expert reports questioning the ministry’s willingness to identify a capacity in the first place, and then to stress-test it.

Public health experts still think that the ability to contact-trace 1000 new daily cases has merit – especially if the more infectious Omicron, having just arrived in MIQ in Christchurch, finds its way into communities.

Verrall said the capacity for 11,000 contacts a day should translate to about 1000 cases, given that casual contacts are not likely to be chased.

But there are two key differences to when she made that recommendation over a year ago: vaccines, and a risk-based system rather than a one-size-fits all approach.

The former means that the risk of an outbreak is much less, even though there remain pockets of unvaccinated communities all over the country.

“I am reassured that the public health risk we face is substantially reduced – tenfold or more.”

That also means that any outbreak is unlikely to spiral out of control as quickly as it would in an unvaccinated population. The timeline has been adjusted accordingly: increasing from standing to surge capacity is spread over two weeks.

The latter means that the new capacity can be spread according to need.

Public health teams working with community groups can be deployed for the types of complex cases that made it difficult to identify cases and contacts in Auckland.

Having a detailed and strategic plan to engage with the marginalised was something that was missing when Delta arrived, despite warnings that an outbreak would see the virus likely find its way into such communities.

Putting such a plan in place is now a priority.

“There’s a lot of work on the vaccination front to make sure there is a deliberate focus in each DHB to reach people accessing alcohol and drug services, or people in transitional housing,” Verrall said.

“In some cases, there’s work being done with sex workers when there’s an organisation who can link health services into the community.

“That has been a focus. And that’s the work the director-general of health has commissioned: to make sure that those lessons about engaging marginalised communities are synthesised and learnt.”

According to data platform Tūtohi, only 72 per cent of the 120,000-odd people who engage with mental health or addiction services are fully vaccinated.

“The other end of the spectrum are people for whom the telehealth method of engaging with contact-tracing works really well,” Verrall said.

Instead of multiple phone calls, interviews, and a nurse entering the information manually into the computer system, there could be an initial phone call explaining the situation.

“Then a digitally-literate person could add all the information on the internet. We’ve also been able to develop an email and daily check-in that allows people to indicate if they want more support.”

A person who diligently used to Covid Tracer app to scan into every location they visited, for example, would easily be able to upload locations of interest.

Verrall said there was still a need to check the isolation milestones, including being tested at certain times and completing the time in isolation.

There will also be little to no focus on casual contacts, given that so few of them test positive in a highly vaccinated environment.

“In some of the lower-risk contexts, we were finding such a low rate of positivity that it ceases to be a justifiable use of a resource, or imposition on the people we’re asking to stay home for seven days.”

She added that the public health units across the country can do up to 1000 case investigations a day.

“All of those capacity improvements have been made. But they won’t work unless we also do the improvements in how we engage with marginalised communities.”

Bluetooth Tracer function of ‘limited value’

Verrall said there were few if any cases in the outbreak that were detected from using the Bluetooth function. The Ministry of Health does not record such data.

The function monitors other apps that have Bluetooth enabled and records contact of 15 minutes or more within two metres.

“At alert level 4 or 3, you’re not standing next to someone for 15 minutes when you go to the only places you’re allowed to go – like the supermarket,” she said.

For the entire outbreak, which has seen a total of more than 10,200 cases, only 178 Bluetooth alerts have been sent to devices telling people they may have been in close contact with a case.

Verrall said the Bluetooth function might be useful in the traffic light setting.

“We think it could still have some value now that we’ve moved out of the elimination phase, but I watch it closely,” Verrall said.

“I’m just aware that we haven’t seen it give the benefit we would have hoped earlier. It’s fair to say it’s been of limited value.”

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