COVID-19 at the borders – Expert Briefing

The SMC led an online media briefing about New Zealand’s efforts to control COVID-19 at the border.

Associate Professor Patricia Priest, University of Otago

The full briefing is available here and an excerpted transcript is below.

Can you give us your perspective on how the system has been working so far and what these new cases might show us?

“Clearly the system hasn’t worked on this occasion. I don’t have any special insights into exactly what happened but it seems that there was perhaps some lack of clarity about what exactly needed to be done in terms of testing of people who had come in before the policy about testing changed. It’s clear that something didn’t go quite right in this particular occasion in terms of allowing people out without being sure that they were negative beforehand.

“I guess it gives us a wake-up call and is telling us that we need to look harder at how we’re managing at the border and being very clear about what the requirements are and ensuring they are carried out.”

In the current state in NZ – for the last few weeks no cases and at the moment only a few cases – what should those measures be like at the border in terms of quarantine and testing? What would be the best-case scenario to make sure we’re catching any cases?

“What we want to do at the moment is stop anybody coming into the community who’s carrying COVID. So it really means we’re looking at really enforcing quarantine and isolation for the full 14 days with testing – and I know that the new strategy is to test early in the period to pick up people who have the virus, and then again near the end to make sure that we pick them up there. So I think if that’s absolutely rigidly adhered to then that’s about as good a protection as we can get.

“The question is how rigidly can we feasibly adhere to it for how long, and given the pressure from people – particularly who have dying relatives – is obviously huge because it’s a really awful situation to be sitting in quarantine knowing you might miss seeing your relative before you die. If we’re thinking purely about how do we keep the virus out of New Zealand we really would have to absolutely rigidly adhere to those requirements.”

At the moment we’re not letting many people in and keeping them in quarantine – it’s that feasible to do for weeks, months, maybe longer?

“I’m not an economist and I’m not a politician, so from the point of view of keeping the virus out that is absolutely what we would need to do. But whether as a country we have to accept that it’s not feasible to do that for the possibly years it might take to get a vaccine is really a decision that will be made based on not only the epidemiology and the transmission modelling but also economic modelling and obviously the political realities. And those decisions are taken way above my paygrade.

“It’s a situation where it’s not black and white, it’s not like: we must do this. If we do the rigid quarantine then we probably will keep it out but the question about whether we can do that and how long we can do that for as a country requires other information.”

Earlier this week we were having quite a bit of discussion: what it meant, when ‘Elimination Day’ would be. Is it a relevant distinction we should be aiming for?

“We’ve gone for an elimination policy which means we are trying to stop the virus from transmitting within our community. Since that’s been our goal it’s fair enough to talk about it. Personally I think it’s a bit of a red herring to say here’s the absolute definition and my goodness we’ve hit it, and tomorrow we might discover we haven’t quite hit it. To me, the focus is: we are trying to ensure there are no chains of transmission going on in the community and we appear to have achieved that. And, as far as we know, we may still have achieved that – we don’t know that these two new cases have transmitted to anybody in the community and if they haven’t then we still have in fact met our own definition of elimination, which is about not having any chains of transmission in the community for at least 28 days. It’s helpful to know what we’re aiming at and it’s helpful to be clear about whether we need to do more to either get back there or to get there, but I don’t think spending a lot of time arguing about exactly what the definition is is necessarily useful.”

Earlier in the year there were questions about whether there was any use of thermal screening at the border, do we know anything more now about whether that’s useful or feasible?

“I haven’t seen any specific analyses for COVID, but as a sort of respiratory illness which has a number of symptoms which are similar to the types of symptoms in flu, I think we can look at studies using thermal scanning to screen for flu at the border. They show, in my view, that it’s not a worthwhile investment of resources in a time when you’re thinking about keeping a pandemic out.

“I co-led a study in 2008 when we were really worried about some of the flus that might come of out Asia at the time where got people coming into Christchurch airport to fill out a form about their symptoms, and then we tested a sample of them to see if they were carrying influenza. And we did a little sub-study where we used thermal scanning machines and then also took their temperature and took a swab. And what we found in that thermal scanning study was that thermal scanners were not too bad at detecting people who have fever, when you measure it using a thermometer, but in that smaller sub-study none of the people who carrying influenza actually had a fever. And then in the larger study we did have some people with fever and with influenza, but of the people who had influenza in their nose and throat only about 2.5% had fever at the time that they came through the airport.

“So you might pick some people up with coronavirus if you do thermal scanning but you will miss a lot and you’ve put a lot of effort in. And the other thing is there were a lot of people with symptoms, including fever, who didn’t have flu and who wouldn’t have coronavirus so you end up having to potentially isolate, while you wait for the tests, large numbers of people in order to pick up a small proportion of the people who are actually infected and meanwhile the rest of them are not detected.

“Personally I think it’s something that governments sometimes do because it makes people feel like they’re doing something, but I would worry about the sense that ‘oh we’re doing what we need to’ and you definitely can’t rely on it to detect all cases coming in.”

Do we know much more about how long people might be infectious before they start showing symptoms?

“The other thing about screening at airports: if you think about the whole trajectory of an infection, it’s thought that – based on the evidence we have from people we’ve analysed – that there’s maybe about five days from when you’re first exposed to when you get symptoms. And you’re probably infectious for two or three of those days before you get symptoms, and then you continue to be infectious for some period after that.

“So if you think of someone who gets infected, it might be 10-14 days from when they get infected to when they stop being infectious. And if you think about, let’s say ten days, 240 hours, if you think about the three hour trip from Australia to New Zealand that’s a tiny proportion of period. Assuming that if you’re sick you don’t get on the plane, the probability that they will get sick enough to be noticed when they get into the airport is quite small. So again you might pick some people up but you definitely won’t pick everybody up.”

What sort of developments would we be looking for to open a border with another country, for instance, a ‘Trans-Tasman Bubble’?

“It depends on the degree of confidence that you’re wanting that we’re not going to get cases. If you want to be absolutely sure that we will not get cases coming into the country then we would really need to only allow people in from countries where there are no cases and we’re confident, because of the testing and contact tracing systems that they have, that there actually are no cases. Which is going to quite a small number of countries, obviously.

“So then you need to start thinking about countries where there’s only a small number of cases and if we let people in from those countries without requiring them to quarantine then we’re taking a risk. It might be a small risk but we would be taking a risk. I guess at some point the appetite for risk will get to a point where we might do that and then see how that goes. You’d be wanting those people who are coming in to be keeping very good records about where they’ve been so if they did turn out to be a case you can be contact tracing them. But we’d definitely want to start with countries with no cases as far as we were aware.

“[Australia] are still having cases – not many, but they are still having cases. So it comes back to being a political decision. They’re on a good trajectory, they may well get to no cases in the next couple of months, but these things are extraordinarily difficult to predict.”