Localised lockdowns could help avoid alert level yo-yoing but they have significant limitations, experts say

Source: 1News

Auckland has spent the last three weeks yo-yoing up and down Covid-19 alert levels, just what Prime Minister Jacinda Ardern set out to avoid when creating the system at the start of the pandemic.

Covid-19 community testing centre.

In that period, New Zealand’s biggest city has twice been at Alert Level 3, for a total of 10 days, as health officials tried to contain the cluster centred around Papatoetoe High School. With options that include localised lockdowns to a revised alert level system, what are experts saying could be implemented to avoid a repeat?

Localised lockdowns could be a useful tool in avoiding yo-yoing up and down alert levels after a lockdown, but they have significant limitations, particularly when a Covid-19 cluster is first discovered, experts say.

With the economic cost of an Auckland-wide lockdown estimated at between $32 and $39 million a day, according to economist Brad Olsen, many Aucklanders have queried if a suburb-by-suburb lockdown could be implemented to limit the economic damage.

Covid-19 data modellers Professor Shaun Hendy and Dr Dion O’Neale say their modelling shows suburban lockdowns would not necessarily be effective in Auckland, particularly at the start of a new outbreak, because Aucklanders are so mobile.

“I think Australia tried some of those postcode lockdowns and they didn’t work well, and the reason they didn’t work well does relate to, it’s not so much that people are travelling long distances themselves and mixing in the city. It’s the people who they interact with in those places who are also travelling from further afield,” O’Neale told 1 NEWS.

Auckland University’s Shaun Hendy says Kiwis need to remain vigilant to keep the virus out of the community.

“Just because you had a person from Papatoetoe who works in Penrose, it’s not the Papatoetoe to Penrose link that matters, it’s everyone who shares an office with that Penrose person and they’re living as far as away as Glenfield or something like that. You very quickly get a huge amount of geographic spread.”

Epidemiologist Professor Michael Baker says there are two different types of outbreaks, ones “that are clearly connected to a source, a border failure,” and “outbreaks where you don’t know where they have come from”.

The latest outbreak in South Auckland was the first outbreak in New Zealand that was difficult to put in one of these two categories, Baker said.

“You’ve got outbreaks that are clearly connected to a source, a border failure, then you’ve got outbreaks where you don’t know where they have come from, you have to assume that there is a chain of transmission beneath the surface that you cannot identify initially,” he said.

”This outbreak is the first one that has been a bit between positions, because when it was first detected it wasn’t clear which type of outbreak it was, so everyone assumed the worst and then it became quite clear after a few days that there was a probable connection with the border and there didn’t seem to be any other cases detected despite high levels of testing.”

Baker said the Government decisions to move Auckland down from Level 3 on February 17, before returning it back to Level 3 lockdown on February 28, were “reasonable”.

“Then the problem came up, and this is a new problem for New Zealand, there wasn’t a large hidden outbreak in the community but there were people who were not, for various reasons, following best practice.

“This is a new thing for us to have to go up the alert levels, not to address a hidden outbreak but actually, as a way of guaranteeing we were able to dampen down downstream transmission.”

Baker co-authored a story on The Conversation with Nick Wilson and Amanda Kvalsvig to mark the one-year anniversary since New Zealand’s first Covid-19 case . The experts from Otago University wrote that “using more geographically targeted and less disruptive ‘circuit-breaker lockdowns’” was one way in which New Zealand could enhance the detection and management of outbreaks.

It was a challenge to nail down a geographical scope for postcode lockdowns, Baker said.

“I do think if you’re doing an area-based lockdown you have to obviously put the ring around a meaningful geographic area and in the case of Auckland it’s quite a big area,” he said.

Hendy and O’Neale say even implementing a suburban lockdown in South and East Auckland a fortnight ago, before Auckland went back to Alert Level 3 at 6am on March 1, would have had limited effectiveness.

This was also the week prior to the revelations that there were interactions by one of the infected families in South Auckland which breached restrictions during the first three-day Level 3 period, starting February 14.

“Of course with this particular case, it was an interaction during lockdown that led to the cluster expanding and so obviously there are limitations on lockdown,” Hendy said.

“It [a suburban lockdown] might be a more useful tool in terms of risk management if you feel like you’ve got a well contained cluster but there are few extra contacts that need tracing. In that situation, you’ve been in lockdown, so you’re confident there haven’t been interactions in the community, in Penrose with people from Glenfield, because you have had that lockdown period, then it could be a useful risk management tool.”

However, O’Neale struggled to envision a scenario where officials had enough confidence to believe the majority of cases were within a small location, but weren’t confident enough to rely on contact tracing to manage such an outbreak.

“You’d need to have some strong reason as to why you thought any potential spread had only happened in that geographic area and it’s hard to have the sort of information that would make you very confident of that but not actually make you confident enough that you could do all of the tracing of exposure events perfectly to just isolate the people who were exposed as opposed to the geographic area around them,” he said.

“You still do what you need to do in the absence of better information, which is close down the smallest area which it makes sense to given the information you have available, which happens to be the whole of Auckland.”

Another difficulty in a postcode-style lockdown was the breaking of more links, O’Neale said.

“Trying to lock down just one postcode, ironically you end up with a worse situation because you are trying to break more links,” he said.

“So people don’t stay within their own postcode, you’re locking down a smaller number of people but of those people almost all of them are travelling as opposed to, at the more absurd level, you lock down the whole of the North Island, you lock down an awful lot of people but you don’t have that many movements from the North Island to the South Island relative to the population of the North Island.

“If you just look at a particular postcode, almost all of that postcode are looking for an exemption because they need to travel to work or get to the supermarket or something like that.”

Hendy said it would be another difficult year as he warned against Covid-19 fatigue.

“We’ve got another difficult year ahead of us so we definitely want to stay on top of our response and we do need to take the country with us, that was one of the things that made us so successful in dealing with the virus last year. I think people are perhaps getting a bit tired of jumping in and out of lockdowns and they can see that the vaccines are on the horizon,” he said.

“We’re going to need to continue to respond strongly to this in the next year, it’s only once we have very good coverage of the vaccine that the risks will start to diminish where we can perhaps relax a little bit and that is some time away.”

Economic cost

The economy overall would still be hit even with the implementation of postcode-style lockdowns, economist Brad Olsen says.

It was estimated that it cost the economy between $32 to $39 million for each day that Auckland is at Level 3, Olsen said.

Infometrics' Brad Olsen says next year will still be a roller coaster ride as the Covid-19 pandemic is not over.

“We also saw and continue to expect that spending activity in Auckland will be down 40 per cent each day and wider across the economy, spending could be down within 10 to 15 per cent.”

The economic cost of Level 2 was harder to quantify, but the looser restrictions were much more industry specific compared with Level 3, with hospitality particularly bearing the brunt of the damage of reduced customer capacity, Olsen said.

Hypothetically, if a quarter of Auckland were to be locked down in a future outbreak, that wouldn’t necessarily equate to the hit to the economy being reduced by 25 per cent.

“Probably not so simply, in the sense that any harder restrictions like at Level 3 on any part of the economy does have wider flow-on effects,” he said.

“You wouldn’t have those workers in that quadrant who might be able to go out to work for example, you wouldn’t have people be able to go into that quadrant of Auckland to do business and so the effects could well be more than just say a quarter, for example.

“I certainly take the point that you would likely diminish the economic shot for a period.”

A revised alert level system that’s fit for purpose

Epidemiologist Michael Baker says our alert level system is no longer “fit for purpose” a year into the pandemic, with a new system to have a particular focus on high-risk indoor events.

Michael Baker says the current plan is a “real weakness” after the latest case wasn’t picked up until being retested.

He was also calling for the implementation of more levels into the system to avoid the “circuit-breaker type lockdown, levels 3 and 4”, that are so damaging.

“We’re using it differently a year on in that we are trying to avoid lockdowns all together, so we’re focused on using it a more nuanced way. We’re also using it in a geographically-targeted way.”

Under Baker’s revised alert level system, more levels would be added with a focus on mask use and high-risk indoor situations, where research showed that the vast majority of transmission occurred.

“My observation would be as soon as people move from Level 3 to Level 2, they might as well be doing nothing, they feel like it’s the all-clear and it’s business as usual.

“I think given the global experience with how it’s spread, there is very little transmission outdoors so really you can resume almost all outdoor activity, but you have a much stronger focus on indoor activity.”

Baker said the addition of new levels would not make the system more complex.

“It would take into account that you do need to do things on a more regional basis and you want to avoid having to tell people you have to stay at home,” he said.

“It’s also saying the three levels below current Level 3 are where we really want to be if we get a problem, so we can ideally avoid Level 3 altogether but to do that you still have to have a very well developed Level 2 system, there would still have to.”

“You wouldn’t have to stay at home but there would be real limits on high-risk indoor gatherings and a strong emphasis on mask use in all indoor environments.

“Less emphasis on physically staying at home and much more emphasis on infection control and minimising the spread of the virus. We haven’t really embraced mask use yet in New Zealand.”

Tackling the new variant

While the effectiveness of suburban lockdowns would be limited, Covid-19 data modellers Shaun Hendy and Dion O’Neale were more confident that a significant outbreak of the new more-contagious UK variant would be more difficult to contain.

“We’re still learning a lot about the is B.1.1.7 [the UK variant] and in fact just before I came on this call, I was reading a paper about it,” Hendy said.

“One of the things we’re almost certain about is it would be very hard to contain if we got a substantial outbreak.

A significant outbreak would require harsher restrictions in order to bring it under control,” Hendy said

“That’s based on observations from what’s happening overseas as well as some of the modelling that has been done. It would require more stringent restrictions should we have a large outbreak of it,” he said.

Coming out of lockdowns also carried more danger when dealing with the new variant, Baker said.

“Certainly, the risk you are taking with opening up earlier with this strain is much greater.”

Contact tracing system

Associate Health Minister Ayesha Verrall told Breakfast last week that the contact tracing system needed improving, as the types of outbreaks in Aotearoa were taxing it in different ways.

With only three positive results from mass testing, physician and MP Ayesha Verrall says the chance of unknown community transmission is low.

Verrall, whose recommendations helped improve the system last before she entered politics, said the system had traced more close and casual contacts in the Papatoetoe cluster than last year’s August cluster, despite there being a fraction of the cases.

“Just remember, of the close contacts that we’ve traced in this outbreak, 87 per cent have been within the 48 hours that I specified as part of the performance criteria for that, which is really key

“We do need to look at how to continue to improve the contact tracing system, when I think back a year ago, I imagine that what we’d be dealing with in New Zealand would be large-scale community outbreaks.

“We do need to remain prepared for that but it seems like the most common scenario for us are these chains of transmission, small numbers of cases but we’re tracing a large number of contacts and that puts different burdens on the system and we need to prepare for it in different ways.

“Just to give you an example, in August last year, we had 150 cases and traced 2,300 close contacts. This time in February so far, we’ve had 15 cases, so a tenth of the number of cases, and traced the same number of close contacts, plus 3,000 casual contacts,” she said.

“We’ve actually used the contact tracing system in a very different way because of this different pattern of cases that we’re getting.”

“I think it is important when the teams have finished their hard work on this event that we have a proper debrief and think what could we do differently to actually reflect how we’re using the contact tracing system and how Covid in reality is being transmitted in New Zealand under the elimination strategy.”

Professor Michael Baker and Professor Shaun Hendy