The data-matching system where the Government checks whether MIQ workers are properly tested failed to detect the case of the Grand Millenium security guard, who should have been tested fortnightly but wasn't tested for five months.

The issue is highlighted in a series of MIQ reports released today by the Government, which highlight how reliant the system is on people to do the right thing, but also how the system failed to do what it was meant to do.

After the security guard tested positive for Covid-19 on April 7, it emerged he hadn't been tested since November, and his behaviour prompted Prime Minister Jacinda Ardern to say he had been lying.

The testing of MIQ workers is meant to be visible on the Border Workforce Testing Register (BWTR), but the register showed that the security guard was compliant with testing requirements until late March.

This is despite the guard, known as Case B, having his last test on November 27, and then being sent reminder texts about his tests from late February.

The BWTR did show the guard was non-compliant for a five-day period in March, but this wasn't because it was working properly, but because of a lack of attendance data, a report from KPMG said.

The employer, First Security in this case, isn't informed when the reminder texts to the worker are sent.

There are also texts or emails sent to the employer about workers' upcoming tests, but this function - described in the BWTR user manual - wasn't live until the end of April, well after the guard had tested positive.

The BWTR also doesn't hold the results of tests, so it is up to workers to tell their employers if they test positive.

The guard tested positive on April 7, but didn't tell First Security until the company called him the following day.

First Security could have discovered the guard had lied about having nine tests between December last year and March this year by running a detailed check.

"However, there was no pretext for doing so because Case B was not showing as being non-compliant on the BWTR 'chase list'," the report said.

It said the BWTR suffered from "delays in uploading data, and delays and inaccuracies in the linking of National Health Index (NHI) numbers with Person Profiles".

Before the guard's Person Profile and NHI number were linked - which happened on March 10 - First Security was unable to independently verify Case B's tests.

He showed as non-compliant on that date.

"The reason for this non-compliance was a lack of attendance data, not because Case B had not actually undergone tests," the report said.

"When Case B had their attendance logged through the WOL system on March 12, and when this data was uploaded, Case B's testing status changed to compliant."

First Security still can't view test dates for around 60 employees because their NHI numbers had not been linked, the report said.

The Government uses the WhosOnLocation (WOL) system - introduced in early February - to match workers at the border against the testing data in the BWTR. Logging into WOL triggers the testing cycle and schedules test dates, which then appears on the border worker's record in the BWTR.

But KPMG said WOL "may not accurately reflect attendance of border workers due, in part, to inconsistent use by individual workers and lack of enforcement at work sites".

The guard first used WOL on February 17, but didn't log on for every MIQ shift.

"WOL was not always enforced by Site Managers or other designated persons, particularly when manual sign-in sheets were also being used."

KPMG recommended site managers confirm the use of WOL, and spot checks to check compliance along with same-day data uploads for testing and attendance data.

"Access to testing is especially problematic for shift workers, particularly those with limited time and means and on irregular rosters. These factors can lead to tests not being taken within specified periods," the report said.

"Although DHBs work with employers to organise testing schedules that suit the realities of shift work, there may be occasions when these schedules do not align.

"This incident presents a timely reminder of the need to reinforce Governmental and societal expectations around border workforce testing. Testing remains a key component in New Zealand's defence against Covid-19."

First Security's internal review showed that border workers were being asked by site managers to complete additional tasks beyond the scope of their duties.

"These additional tasks included cleaning down high-touch, common areas, such as lifts. Such tasks potentially exposed these workers to greater risk of infection."

First Security has now introduced daily audits of the BWTR against attendance records, and reiterating the importance of using the WOL system.

Head of MIQ Brigadier Jim Bliss said a number of recommendations have been made, and action in response is well underway.

The BWTR and WOL systems had been improved, and it was now less of a high-trust model, he said.

Other reports released today were into the probable aerosol transmission in the hallway at the Grand Millennium and via the ventilation system between floors at the Grand Mercure in Auckland.

There was also a breach of protocol on the bus to and from exercise areas by those staying at the Grand Mecure.

The Grand Mercure and Grand Millennium in Auckland will remain unoccupied until their ventilation systems are upgraded and they can more safely house people coming to New Zealand from overseas.

"Remediation work at the Grand Mercure is almost complete. An extensive assessment of the Grand Millennium's ventilation system has been done and a remediation plan is being developed," Bliss said.

"A programme of extensive reviews and remediation of ventilation systems across all managed isolation facilities is underway."

Those included removing barriers to access testing, and continuing to improve data management systems.

Director-general of health Ashley Bloomfield stressed that the overall risk of Covid-19 leaking from MIQ into the community remained "very low".