Certificates stating a returnee has tested negative for COVID-19 prior to their departure are "difficult, if not impossible" to validate, according to a spokesperson for the Ministry of Health.
Questions are being raised regarding the authenticity of pre-departure test results, a requirement under the Government's strict set of entry conditions. Prospective returnees must present a dated certificate confirming they have tested negative for the virus within the 72 hours prior to their flight.
However, a vast number of returnees are testing positive for the virus either on arrival or on their first day in a managed isolation facility - also referred to as day 0/day 1 testing. On Monday, 10 people travelling on the same flight from India returned positive results on day 0/1 - despite being required to present evidence of a negative result just three days prior.
The data is fuelling concerns that returnees could be using fake certificates to enter the country.
On Monday, University of Auckland microbiologist Siouxsie Wiles said she was aware of one returning New Zealander who had been offered a fake 'negative test result' certificate in Europe.
Wiles said she has "no doubt" that "unscrupulous people" are offering fake certificates for a fee.
Speaking to reporters on Monday, Prime Minister Jacinda Ardern said the Government has not seen any evidence of fraudulent testing data at the border.
She also pointed out the possibility of returnees contracting the virus after undertaking their pre-departure test.
"What seems to be the case at the moment is we have some countries where outbreaks are significant, and after people are being tested pre-departure, they're becoming sick," Ardern said.
The Government has never considered pre-departure testing to be a "foolproof" measure, she added.
"That's why as soon as someone arrives in New Zealand, we test them immediately again."
However, a spokesperson for the Ministry of Health told Newshub pre-departure test results are "almost impossible" to verify and fake certificates are "challenging" to detect.
Certificates are "very difficult" to authenticate as testing regimes - and their reliability - can vary country-to-country.
"This means if fraudulent test results are used, they are challenging to detect and very difficult to enforce," the spokesperson told Newshub.
The Government accepts results obtained from PCR tests, antigen tests, also known as viral antigen tests, and tests using loop-mediated amplification (LAMP) technology, they noted. However, not all tests are created equal - which can lead to inaccuracies.
"Not all tests are the gold standard PCR tests we use in New Zealand because they aren't available or accessible everywhere."
The efficacy of pre-departure testing has also come under scrutiny as a negative result within the 72 hours prior to departure does not account for incubation.
Experts have pointed out that an individual could be harbouring COVID-19 at the time of their test, but are not presenting enough of the virus to return a positive result. Pre-departure testing also does not account for the possibility of a returnee contracting COVID-19 in the days between the test and their arrival in New Zealand.
However, the spokesperson said the number of returnees testing positive for COVID-19 shortly after their arrival is not necessarily indicative of an issue with pre-departure testing.
"People may not have been infectious when tested before travelling, as they may have still been developing the virus, or they might have picked it up en-route. A traveller can return a completely authentic negative test before travelling, but won't catch a diagnosis particularly during the early stages of infection," they said.
The Ministry of Health's Director-General, Dr Ashley Bloomfield, has confirmed the Government is assessing the pre-departure testing regime.
Although "very few people" have returned to New Zealand without evidence of a pre-departure test, he reiterated the nature and the reliability of testing "varies around the world".
"That's why day 0/day 1 testing was put in place. [It] appears to be catching some cases earlier than would otherwise be the case, which is a good thing."
The spokesperson said the ministry is not treating fake pre-departure test results as a "significant issue".
According to Customs' data, there is little evidence of non-compliance since the requirement for pre-departure testing was introduced on January 15.
Between March 1 and March 25, only five returnees have been given warnings for issues with their pre-departure test certificates. Only one person has been prosecuted or issued an infringement notice regarding their test data this month, on March 3.
The pre-departure testing requirement came into effect in late January as an additional layer of protection at the border.
Before entering New Zealand, returnees must present evidence of a negative test processed by an authorised or accredited laboratory in their country of origin. The laboratory will then issue the recipient a dated report containing specific information, such as their name, date of birth and/or passport number, the name of the testing lab, the type of test, the date and time the test was conducted and the result of the test.
Initially, only those returning from the United States and the United Kingdom were required to provide evidence of a negative test before travelling. However, that was expanded shortly after the first announcement to encompass all returnees worldwide - with limited exemptions.
The spokesperson confirmed legislation is in place to penalise returnees who provide a fraudulent test result. Under the Act, an infringement fee of $300 can be issued. If the individual is prosecuted through the courts, they can be fined up to $1000.