Covid-19

One week to get contact tracing in order

Analysis: With the lockdown lifting in a week's time, a new report shows the Government has a lot of work to do in order to build up the robust contact tracing regime needed for a safe transition to Alert Level 3, Marc Daalder reports

Jacinda Ardern has announced the country will be leaving lockdown in a week's time and the pressure is on for the Ministry of Health to improve its contact tracing regime in the interim.

A damning audit of the Ministry's ability to contact trace the Covid-19 pandemic shows the Government has a lot of work to do before it's safe to transition to Alert Level 3. 

The report, by University of Otago Senior Lecturer Ayesha Verrall, an expert in infectious diseases with a focus on contact tracing, has found significant gaps in the existing contact tracing system, including slow processing times and workloads that exceed the capacity of underfunded Public Health Units.

Verrall also outlined the steps that will be needed to get New Zealand's contact tracing regime to where it needs to be. Contact tracing is important because, alongside testing, it forms the backbone of any epidemiological response to Covid-19.

Without fast case isolation after restrictions ease, modelling shows the virus could spread exponentially and ultimately kill 100,000 Kiwis. The lockdown would have merely delayed the inevitable.

While New Zealand's testing regime now appears to be one of the best in the world, the other component of case isolation is quarantining everyone who came in contact with a Covid-19 patient. These people are to be treated as suspected cases and remain home for 14 days, at which point they'll be declared free of the virus. If they develop symptoms, they'll be tested. If they test positive, then their contacts, too, will have to self-isolate.

This is the fundamental principle of Covid-19 epidemiology and the best bet the country has for staying on top of the virus.

"Rapid case detection and contact tracing, combined with other basic public health measures, has over 90 percent efficacy against Covid-19 at the population level, making it as effective as many vaccines. This intervention is central to Covid-19 elimination in New Zealand," Verrall wrote in her report.

Director-General Ashley Bloomfield said on Sunday the country's tracing system would be "gold standard" within a week.

For Verrall, that standard would have to be scalable and "able to respond to exponential growth in case numbers"; fast; effective, in which "contacts will adhere to the self-isolation direction and onwards transmission from contacts will be rare"; equitable with high performance across age and ethnicity; and acceptable or amenable to both the contacts and the health officials using the system.

Report's findings

The current system isn't there yet, Verrall found.

Among the highlights of the report's findings are that Public Health Unit capacity is far below where it needs to be.

"The capacity of the 12 Public Health Units (PHUs) in New Zealand is the primary factor limiting New Zealand’s ability to scale up its case management and contact tracing response to Covid-19. In March the workload of PHUs exceeded their capacity to conduct rapid contact tracing on occasion, even though case numbers were less than 100 per day," Verrall wrote.

In response, the Government launched the National Close Contact Service (NCCS), which can take on overflow from PHUs, particularly where a centralised approach is suitable and a regional touch is not needed. Even so, however, New Zealand's public health teams were still overwhelmed as the lockdown began.

"When New Zealand moved to Alert Level 4 on 25 March, many PHUs were at or beyond their capacity to manage cases and contacts, even with increasing support from the newly established NCCS. During that week, nationwide daily case numbers ranged from 70-86," Verrall found.

"Some PHUs have since expanded their contact tracing workforce on a temporary basis – drawing on staff normally involved in vaccination and school programmes – but this is unlikely to be sustainable once routine public health work recommences when the Level 4 Alert is lifted. Even these temporary increases are insufficient for the likely future workload."

Verrall also found the process of referring contacts to the NCCS resulted in delays for tracing.

"Initially, the timeliness of the process was poor. For, example between 2 and 8 April the average time from referral to instructing a contact to isolate was 2.3 days. However this likely reflected the staff training and software changes that were occurring at the time," she wrote.

"At the time of my audit the main remaining quality concern was that only 60 percent of contacts could be easily reached by phone, either because of incorrect contact details or because people choose not to answer calls from an unidentified number."

These latter problems are now being addressed, with the National Health Index being linked to other health databases to provide more reliable contact details and a new system that will show calls from contact tracing teams as coming from a local number. By the end of April, all missed contact tracing calls will be followed up with an explanatory text message.

Centralised or decentralised?

One of the crucial questions facing the Government is where on the spectrum between centralised and decentralised contact tracing it wants to set itself. As it stands, the PHUs each administer a specific region while the NCCS takes on overflow from centralised call centres. However, officials in the PHUs are loathe to refer some contacts on to the NCCS, Verrall reported.

While "Medical Officers of Health I interviewed were broadly supportive of the concept of a ‘hub’ and agreed the NCCS could be an important part of measures to deal with the intense workload they faced in the last half of March", "they were cautious about diverting contact tracing to the NCCS in many situations, because once they did they lost visibility of the outcome for the contact".

The National Contact Technology Solution (NCTS) is a cloud-based platform that "stores case and contact details linked by exposure events, and supports contact management. It provides links to existing health information sources, primarily for sourcing contact details and the unique identifier from the National Health Index". The NCTS helps the centralised NCCS operate smoothly but isn't currently accessible by PHU staff, Verrall found.

This meant PHU staff could lose sight of contacts referred to the NCCS, even when knowing the results of that tracing could prove important for their localised efforts.

There were three scenarios in which PHU staff preferred to trace contacts locally: when the contacts themselves had numerous contacts, because of the potential for a cluster-style outbreak; when a contact was "medically complex" and could not be assessed by a call centre; or when there was transmission in an institutional setting like a rest home or school and a hands-on approach was required.

"For a greater proportion of contact tracing to be diverted to the NCCS, Medical Officers of Health would need to have access to the NCTS to be confident that the contact is traced in a timely way. This is particularly important for cluster management as otherwise second or third generation spread can be missed," Verrall wrote.

"PHUs would also need to be confident that the frequency of followup was appropriate for higher risk contacts. These areas need to be discussed further between PHUs and NCCS and appropriate triage processes and protocols refined. The underlying technology (NCTS) will also enable delegation of a case to the NCCS but this process will need to be very carefully defined, as cases need clinical care and are the highest risk group with respect to transmission."

Expanding public health capacity the key recommendation

In the end, Verrall produced eight recommendations, many of which the Government has said it is in the process of fulfilling.

The first is to expand the capacity of PHUs and the NCCS such that they are able to, in a short period of time, scale up to tracing all of the contacts of 1000 cases each day. This represents a three- to four-fold increase in contact tracing capacity for PHUs.

"The Shincheonji church outbreak in Korea in late February/early March rose to over 4482 cases in less than three weeks. Such situations pose a challenge for planning because exponentially increasing demand will need to be met in a short period of time," Verrall wrote.

"Case isolation and contact tracing remain effective against Covid-19 even during large outbreaks. Therefore as a matter of preparedness there must be a plan to rapidly scale PHU and NCCS capacity to manage up to 1000 new cases a day if needed, while maintaining the essential performance quality to minimise the chances of transmission beyond identified case contacts."

In response, the Government has announced a funding boost to the tune of $55 million for PHUs. The announcement comes after the public health teams were given an additional $40 million in March, including $15 million specifically for contact tracing, and now means the original $47 million annual budget for PHUs has more than tripled in the span of two months.

"This funding will mean PHUs can be expanded as required, with additional surge capacity of up to 300 full-time equivalent staff. The NCCS will also get extra resources to manage complex investigations, such as detailed analysis of clusters," Health Minister David Clark said in a statement. Clark said PHUs can currently only trace around 185 cases a day, while the NCCS has capacity to make 5000 calls a day but that could be doubled in a short period of time.

Key performance indicators

The remaining recommendations have more to do with preparedness than capacity. Verrall called on the Ministry of Health to develop a plan for outbreak response "that includes how to rapidly scale case identification and contact tracing and regain control. The plan should specify the task-shifting arrangements between PHUs and NCCS and any additional resource required to deal with up to 1000 cases per day while maintaining high performance."

She also wanted to see the NCCS and PHUs make sure every self-isolating contact was contacted on a daily basis. The NCCS and Medical Officers of Health need to hash out referral protocols and triage systems, especially for the sort of high-risk or medically-complex cases outlined above. PHUs should be given access to the NCTS in order to improve coordination. The Ministry should work with PHUs to see if the NCTS could be used as "a single national contact information system" for contact tracing for Covid-19. 

One of the last recommendations is the development of a system that monitors case isolation from onset of symptoms to the quarantine of contacts and measures progress against key performance indicators. Verrall proposed 17 indicators, including three of critical priority and three of urgent priority.

The three most important metrics were the ability to scale up over the course of five days to tracing 1000 cases and their contacts each day, the tracing of 80 percent of contacts of cases and the quarantining of these 80 percent within four days of the index case first getting symptoms.

Verrall said this latter information was not currently available. "Data on this measurement was not available during my audit because the current monitoring system will not provide visibility of the upstream events relating to case management. The time taken to be assessed clinically, tested and notified of results should be considered components of a single system, and measured and managed accordingly," she wrote.

Three other crucial metrics would be reporting test results of 80 percent of positive cases within 24 hours, isolating 80 percent of contacts within 24 hours of their being identified and ensuring fewer than 20 percent of contacts have Covid-19 at the time they are traced.

A smartphone app for contact tracing?

Verrall's final recommendation is to "rapidly complete development of a smartphone app to assist contact tracing and pilot it in New Zealand".

She said the Ministry was currently working with local developers to create an app based on Bluetooth technology, much like Singapore's much-touted TraceTogether app, but because details were sparse she could not specifically evaluate it. Newsroom has previously reported on the reasons for digital contact tracing and the options available.

"The primary way in which smartphone technology could support contact tracing is through Bluetooth detection of close contact between people’s smartphones and, if one is later found to be a case, instantaneously notifying contacts of their exposure and the need to self-isolate. There is also the potential to use QR-codes to ‘check in’ to high traffic settings like public transport or cafes. This latter function has received less attention but seems particularly important as many clusters appear to arise from transmission in closed crowded environments," she wrote.

"Together, these features could identify contacts that would be missed by manual methods due to poor recall or anonymous contacts in a crowded venue. The time from case diagnosis to contact isolation could also be reduced."

However, Verrall conceded there were flaws with the Singapore model, including low uptake.

"Potential impact will not be realised unless it is acceptable to a large proportion of the population and enjoys high uptake. Less than a fifth of the Singaporean population downloaded the TraceTogether app in 10 days, which, assuming random mixing, means only 1 in 25 exposures will be captured by the app and public health impact will be negligible."

Newsroom reported on Friday that the Government is also considering distributing a Bluetooth-enabled CovidCard to every New Zealander, which would be voluntary to carry around and use and would securely track who the user came in contact with. This information would be deleted after 30 days or released to the Ministry of Health if a user tested positive for Covid-19. The CovidCard would sidestep difficulties with different operating systems and the friction reducing uptake, but would also face roadblocks of its own, including the logistical challenge of quickly manufacturing and rolling out five million high-tech devices.

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