Pre-departure testing fails to take flight
Pre-departure testing seems to have had little impact on the number of Covid-19 cases being detected at the border, data journalist Kate Newton reports.
Since January 15, people coming to New Zealand have been required to test negative for Covid within three days of boarding a flight.
Has it made a difference to the number of people testing positive in managed isolation?
In the 21⁄2 months prior, the average (mean) case rate was 0.66 new cases per 1000 people in managed isolation and quarantine (MIQ). In the following 21⁄2 months, the daily rate has fallen – but only slightly – to 0.55.
Even this negligible drop may have little to do with pre-departure testing.
Since mid-January, there has been a decline in the rate of new cases emerging in many countries, including the UK – the most common origin of returnees.
And this analysis does not include the most recent spate of cases at MIQ, which prompted the Government last week to halt arrivals from India until April 28.
The Government introduced pre-departure testing after pressure from scientists and Opposition politicians.
The policy requires all travellers except those from Australia, Antarctica and some Pacific Island nations to produce a negative test result within 72 hours before their departure to New Zealand. At the time it was introduced, Covid-19 Response Minister Chris Hipkins said the change would add complexity for people wanting to come home but would strengthen New Zealand’s already ‘‘stringent border protection measures’’.
Director of research cluster Te Pu¯ naha Matatini, Shaun Hendy, whose group has modelled Covid19 spread in New Zealand since the beginning of the pandemic, says his colleagues tried to assess the effect of pre-departure testing late last year.
Their modelling suggested it would catch an extra 10 per cent of cases but ‘‘there was a lot of guesswork in there’’.
‘‘It’s difficult to know whether the change [in case rate] is due to the policy or due to changes in prevalence in the UK and other countries.’’
Either way, the testing is ‘‘probably not having a huge impact and that’s consistent with our expectations from the modelling’’, Hendy says.
‘‘To really get at this you’d need to know how many people were not boarding flights because of positive tests and I don’t know if anyone really has that data.’’
Director-General of Health Ashley Bloomfield told media last week it was ‘‘hard to collect’’ data on how many people were not travelling because of a positive predeparture test.
He did say, however, that about 25 people had given up their MIQ spot since the beginning of the year because test.
Bloomfield insists pre-departure testing ‘‘is providing value’’, some of which ‘‘is intangible’’.
‘‘For many people, the opportunity to travel here, the cost of the flight, the procedure and requirement and wait to get a voucher for MIQ; means they don’t want to put that trip in jeopardy. So their actions and behaviours prior to travel are likely to be modified to reduce the risk that they will not be able to travel.’’
An MBIE spokesperson was unable to confirm whether the MIQ cancellations Bloomfield spoke of accounted for all people who tested positive before their of a positive predeparture
flight, as providing a reason for cancelling was voluntary.
University of Canterbury statistics professor and Te Pu¯ naha Matatini principal investigator Michael Plank says the everchanging global situation makes it ‘‘tricky’’ to measure the effect of the policy.
He still believes pre-departure testing is ‘‘useful and justifiable’’ but agrees there’s a lot of uncertainty built into the policy.
‘‘There’s a three-day window before they depart and then there’s also the risk of transmission during the journey . . . It’s certainly not to be relied on as a catch-all.’’
Recent returnee Tenani French says that reliance on individuals makes the policy worthless.
‘‘Not even asking people to selfisolate between the test and departure kind of defeats the point, because the minute you leave the testing centre you could come into contact with someone who has [Covid].’’
The requirement only adds complexity and cost to an already arduous journey home, he says.
‘‘Just getting the test and the flight and the MIQ slot all lined up is like trying to herd chickens. If anything comes apart then you have to start again.’’
French was able to access free testing in California before he flew to Auckland in January but testing was neither free nor easy to access in other parts of the US and in many other countries, he says.