Experts have criticised country’s contact tracing and testing systems as the Government transitions away from elimination.

The Ministry of Health hasn’t increased contact tracing capacity since it was criticised by an expert review in June, even though the new Covid-19 suppression strategy could see the tracing system overwhelmed.

The Government will have to rapidly increase its capacity to contact trace, after failing to do so despite the recommendations of several critical reviews of the tracing system.
The Government will have to rapidly increase its capacity to contact trace, after failing to do so despite the recommendations of several critical reviews of the tracing system.


Philip Hill, a public health expert at the University of Otago and one of the authors of a series of critical reviews of the contact tracing system, told Newsroom the ministry appeared to be “at odds” with a ministerial directive to increase capacity.

One such report, which reviewed the response to the February outbreak and was released in July, found “New Zealand would struggle to maintain high system performance of contact tracing for a prolonged period with 100-200 cases per day”.

At issue is a recommendation dating back to April 2020 that the Government be able to trace the contacts of 1000 new cases a day. That recommendation came from Ayesha Verrall – then a public health expert at Otago, now Associate Minister of Health – and was based on an assumption that each case could have as many as 36 contacts per day.

The Ministry of Health has been loath to create that sort of surge capacity. Under the elimination strategy, it was unlikely New Zealand would ever reach those kinds of case numbers. But with the transition to suppression, in which ministers no longer expect to reduce the number of cases in Auckland to zero, there will always be the risk of an outbreak spiralling out of control.

A spokesperson for the ministry insisted its current surge capacity – to handle 6000 new contacts each day – is aligned with the 1000 cases per day threshold, if each case has six contacts.

This figure is unchanged from the start of the outbreak, showing that despite the transition to suppression, no improvements have been made to contact tracing capacity.

The problem is that, over the course of the current outbreak, each case has produced at least 28 contacts on average. That means the current contact tracing capacity is able to handle just 214 new cases a day – a number the country could well exceed under suppression.

Moreover, if restrictions continue to relax in Auckland, more contacts are likely to be generated as people go out and about.

The 612 cases identified in the first two weeks of the outbreak – most of whom had been infected during Level 1 and visited locations of interest during that time – produced an average of 56 contacts each. Under that scenario, contact tracers would be overwhelmed if daily cases rose too far above 100.

“If the number of contacts the ministry can trace is as you describe, then it appears that they have not increased the capacity of the test and trace system since our last report, which was submitted on June 4 to the minister,” Hill told Newsroom.

“We specifically presented a benchmark calculation around 10-30 contacts per case, which means that if there are 1000 cases per day, then 10,000 to 30,000 new close contacts per day should be able to be managed by the system. This would equate to something between a Level 2 and 3 alert level situation. There are some complications around the way the ministry has recently defined casual contacts as close contacts, but the benchmark calculation is a good reference for estimating system capacity.”

In other words, the ministry’s current surge capacity might be five times smaller than what is needed.

Hill had expressed concern earlier in the present outbreak, when contact tracing was slow to scale up and thousands of potential contacts of Covid-19 cases had yet to be contacted more than a week after they were first exposed.

“We previously warned in each of three previous reports since mid-2020 that New Zealand would struggle to deal with a significant outbreak if capacity wasn’t increased substantially,” he said in August.

“We have not seen how this has been addressed since the report submitted in early June this year.”

The expert went further in his comments to Newsroom on Thursday, saying the expert review panel he sits on reached out to the Public Service Commissioner over the ministry’s refusal to implement a ministerial directive on the 1000 cases per day benchmark.

“We were concerned enough about the decisions the ministry had made about capacity being at odds with the ministerial directive, that we sought assurance from the head of the public service, Peter Hughes, that he would check whether this was appropriate and take action accordingly,” Hill told Newsroom.

Contact tracing is not the only system to come under scrutiny in recent days, as the Government prepares to transition to handling more Covid-19 cases in the community.

New Zealand’s testing strategy was a focus of a critical review released by the Government on Thursday. It found the Government had been slow to debut new testing technologies, like saliva testing or rapid tests. It also recommended the creation of a new testing strategy for New Zealand, now that we expect to see more cases in the community.

On Thursday, Verrall said she didn’t know when the new strategy might be released. But it will have to contain some changes – not just on more widespread use of new technologies but also of targeting testing to the areas and cases that need it most.

Past outbreaks have seen a surge of testing and long queues of cars outside testing centres. That sort of reaction is understandable but not sustainable if there are always cases popping up in the community. Instead, testing will need to be targeted at the most concerning outbreaks and at the contacts most likely to turn into new cases.