Covid-19 NZ: How viable is New Zealand’s coronavirus elimination plan in the time of Delta? | Stuff.co.nz

Covid vaccination rates are far too low to protect New Zealand from the highly infectious Delta variant of the virus. That’s why we’re back in lockdown. But will they ever be high enough? Keith Lynch examines the future for our elimination strategy.

Last week it was announced Fortress New Zealand would, in a few months time, lift the shutters and take those first tentative steps back into the rest of the world.

The plan was both (understandably) cautious and extremely ambitious. Simply put, the game out there has changed.

The Delta variant is so contagious that a number of leading British scientists have exclaimed that the golden goose, the conclusive way out of this pandemic, herd immunity, is now beyond reach.

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In the United Kingdom, the vaccine roll-out has successfully severed the relationship between case numbers and death. About 77 per cent of the British adult population (about 60 per cent of the total population) is now fully vaccinated. Deaths are way down from the January peak. Yet, there’s still some 25,000 cases daily – the disease has certainly not been vanquished.

This illustrates how ambitious Aotearoa’s “stamp it out” approach is – as does the emergence of Delta in the community.

The New Zealand scientific consensus is that we have to try. Giving up means there will be no going back.

Is elimination viable, even after enough people have been vaccinated? What kind of protections will those vaccines provide? Can we make Covid-19 like the measles? And what are the hard questions we need to ask?

5 million (or so) little fortresses

We know one thing for sure: the Delta variant spreads with terrifying ease.

Aotearoa has primarily protected itself through robust border controls, a suit of armour, if you will, around the country. A successful vaccine roll-out will change the dynamic somewhat – we’ll all have our little individual coat of armour, protecting us and slowing down transmission.

The first question then must be: how effective are these little coats of armour? There’s a wide array of studies exploring how the vaccines perform at doing three key things:

• Preventing someone being infected.
• Stopping transmission of the virus.
• Preventing serious illness and death.

The reality is our understanding of the vaccines’ performance has changed because so too has Covid-19. When the vaccines were developed, other variants were dominant. Now Delta is on top.

For example, initial vaccine trials suggested the Pfizer vaccine was excellent at stopping the virus from spreading from person to person and at stopping serious illness or death.

Recent studies suggest the vaccine may be less effective at stopping the spread of Delta, but still incredibly good at stopping people from getting very sick or dying. It’s a bit like a coat of armour that may not stop bumps, bruises and scrapes, but significantly reduces your chances of being stabbed to death.

As this piece from US publication Vox outlined in February, almost all the early talk about vaccines was about how good they are at stopping the virus, not how good they were at preventing the worst outcomes.

This has always been the most important thing. The reasons countries went into lockdowns was not necessarily to stop the virus spreading – no, the toughest restrictions were put in place to stop deaths.

What about transmission?

In July 2021, 469 cases of Covid-19 were identified in what became known as the Provincetown or Barnstable County cluster in Massachusetts in the United States. This happened during a celebration for the gay community, where the town’s population swelled significantly.

According to a US Centres for Disease Control and Prevention (CDC) paper examining the outbreak, of those 469 people, 74 per cent were fully vaccinated. This sounds extremely alarming at first glance. But it’s a touch misleading.

The paper only identifies those who were infected and not the vaccinated people who avoided infection because of the jab. As no vaccine is perfect, it’s vital to remember when the vast majority of people are vaccinated, the majority of cases and deaths will probably be in vaccinated people. Think of it this way, if everyone in New Zealand is fully vaccinated a year from now, 100 per cent of new Covid-19 cases will be in vaccinated people.

Back to Provincetown. As a lot of people were visiting the town, it’s hard to know precisely what the vaccination coverage was when the outbreak occurred. But it may well have been somewhere between 69 to 85 per cent of people fully protected.

What else do you need to know about this case? Well, five people were hospitalised. No one died, which very much reinforces the effectiveness of the vaccines.

There’s one other thing in the Provincetown report that caught the eye. It suggested, with a lot of caveats, that the viral load (the amount of Covid-19) in the vaccinated and unvaccinated people who caught the virus was similar.

Public Health England subsequently echoed this in a statement of its own, suggesting there were signs that people vaccinated against Covid-19 may well be able to transmit the virus like those who haven’t been vaccinated.

To be very clear: this does not necessarily mean all vaccinated people are as likely to spread the virus. Vaccinated people are still less likely to be infected in the first place. And despite these warnings, another study from the UK suggests vaccinated people have a smaller viral load on average.

Paul Hunter, professor in medicine at the University of East Anglia and an expert in infectious diseases, told Stuff: “None of the vaccines will be able to stop the Delta variant [spreading]. The latest data on double vaccinated people in the UK is that vaccines are only 49 per cent effective at stopping infection.”

On this, Professor Michael Baker makes the point that we still do not understand the full potential of the vaccines. As I mentioned earlier, 70 per cent of UK adults are vaccinated, but only 60 per cent of the entire population. Vaccinating children, for example, may well further mitigate the spread of the virus.

Remind me, what is elimination again?

Firstly, it isn’t a case of the borders being shut one day and fully open the next. The government’s plan, which you can see in the document below, is obviously more nuanced.

The definition of elimination right now is this: zero tolerance for new cases, rather than a goal of no new cases. According to Sir David Skegg, the Government’s lead advisor on reopening, elimination is a process, not an outcome. It’s not necessarily about zero Covid. It’s about clamping down hard when cases pop up.

This is why the country is in Level 4 right now. Post mass vaccinations, it’s hoped less restrictive tools are necessary.

There is no doubt that elimination was the right choice at the start of the pandemic and the right choice until we have the vaccine alternative. New Zealand has seen mercifully few Covid-19 deaths, a fairly regular social life, and a thriving economy. (Whether the economy is propped up on an unsustainable sugar rush of cheap money and mind numbing house price hikes is open to debate.)

All that said, there is a widespread acceptance that the borders must open again, that such a move is both just and necessary. And as Skegg notes, Covid-19 is rampant around the world so when we start reopening the borders, the virus will creep in.

“Our allies have let us down. Many countries that could have eliminated Covid-19 either never tried, or threw in the towel,” he says, pointing to the challenge ahead.

The country needs to vaccinate “enough people” (as the government describes it) to allow border opening. The government will not say what “enough people” actually is. New South Wales has signalled it will look to ease lockdowns once 70 per cent of its population is vaccinated.

It’s not that cut and dry for Prime Minister Jacinda Ardern. There’s no magic number, publicly at least. She wants good regional spread of the vaccine, high vaccination rates in high-risk populations, and good uptake for younger Kiwis who have large social circles.

But what if the vaccine doesn’t reach “enough” people? Do we remain as is indefinitely, held hostage by those who don’t get it? We don’t know.

After “enough people” are reached, the government will seek to reopen. For people arriving here, there’ll be tests, and a range of other considerations: a person’s vaccination status, and the risk-profile of the country they’re coming from. Some people will end up in MIQ. Some will no longer need to.

We’ll make it like measles, then?

Ardern has said Covid-19 could be treated like measles has been for years.

“Measles is both incredibly infectious but also potentially deadly for a young unvaccinated child. When we have outbreaks in New Zealand, we contact-trace, and we isolate. These are the public health tools that in the absence of lockdowns, we will absolutely continue to use,” Ardern said.

Is this a valid comparison? A number of international experts I spoke to said no. The main reason being the measles, mumps and rubella (MMR) vaccine used to combat that virus is much more effective at preventing infection. According to the Ministry of Health, after one dose of the MMR vaccine, about 95 per cent of people are protected from measles. After two doses, more than 99 per cent of people are protected.

The Covid-19 vaccine is a bit like Swiss cheese, whereas the MMR vaccine is a block of cheddar.

What’s more, the MMR vaccine has been available since 1969 in New Zealand. That’s not to say New Zealand has won the war on measles. We do have about 70 per cent coverage in children. But we don’t have herd immunity. There are still many younger people – particularly Māori and Pasifika – that are under or un-immunised. This was evident during a significant outbreak in 2019.

But because of the MMR vaccine, measles is much more likely to hit a wall somewhere and stop. Skegg’s advice to the government pretty much acknowledges this.

Hunter says: “Measles is controlled because you can achieve herd immunity if you vaccinate about 95 per cent of the population. Measles then no longer circulates. Coronaviruses will circulate forever and never go away. Indeed, whether vaccinated or not we will expect multiple repeat infections throughout the rest of our lives.”

Then how do we stop it?

Again, it’s widely accepted the snap Level 4 lockdown currently in place was the right call to slow down Delta. But one overseas expert emailed me on Wednesday morning saying Delta is simply too tough to stop. “If they manage to stop this one spreading, another case will pop up somewhere else. But when you are trying to roll out the vaccine then time is what you need.”

Remember the Reproduction or ‘R number’? It’s the average number of people that one infected person will pass the virus on to. When the R number is above 1, the virus is spreading. If New Zealand wants to stop this outbreak, or a future one, it needs to get that number below 1.

The problem we now face is vaccinations alone may not push the R number below 1. That said, and it’s important to be very clear on this, the vaccines will unquestionably reduce the death toll. But they might not be enough on their own to sustain elimination.

Where does all of this leave us? Well, there are, of course, public health measures. The likes of world-class contact tracing, mandatory scanning in, obligatory masks can push the R number down.

Prof Francois Balloux, director of the University College London Genetics Institute, told Stuff a combination of widespread immunisation and public health measures was a “reasonable” plan and the key issue would be reaching vaccination rates approaching 80 per cent.

That kind of number combined with public health measures could keep Delta in check, he says.

But what then? The problem, he says, is you need to keep that going indefinitely. “What’s the end point? Is that for 10 years, 15 years, 20 years?”

He makes the point that it would be psychologically difficult for New Zealanders to accept the disease, even post vaccination. But adds that a willingness to accept public health measures will likely wane if Delta is present and deaths and hospitalisations are low.

Professor Dale Fisher, senior consultant at Singapore’s National University Hospital (NUH) Division of Infectious Diseases, (and a health professional who Associate Health Minister Dr Ayesha Verrall has previously worked under) said of using such public health measures: “Is that the plan forever?”

It was quite notable that Ardern has not ruled out using some sort of lockdown even after mass vaccination.

Such a move would be politically challenging, and according to Hunter, it might not even be enough to curb Delta.

“Lockdowns by themselves are unlikely to be enough to control the spread of Delta; it is just too infectious unless they are really, really strict. The virus is just too infectious. Yes, you can manage localised outbreaks for a while but when it has started spreading widely it gets very difficult.”

He adds New Zealand is in a bind now and will remain there until the vaccination rate is well up.

“Now the functions of lockdowns, at least in low vaccination countries, are primarily about delaying the peak long enough to enable vaccination of all vulnerable individuals. Vaccinations do not stop the spread of infection, but they do reduce the R number, so slow the spread quite a bit.”

Some other things to think about?

There are trade-offs the country as a whole, particularly our leaders, need to consider.

It is, of course, ethically correct to wait until everyone has had a chance to be vaccinated before reopening. And so far the sacrifices the country has made have made sense to save lives. But there have been sacrifices. For example, it’s incredibly difficult for New Zealanders to find a way back into their own country right now.

It’s worth considering this: will the vaccines’ effectiveness at neutering the worst outcomes change those dynamics? Take the example of a similar size country, Ireland. It is still seeing about 1500 cases daily, about 50 people are in ICU but it has a seven-day average of one or two deaths. Sixty-three per cent of the population is fully vaccinated. It’s mostly open, although there are significant public health measures in place.

It’s likely case numbers will rise in Ireland as winter approaches. And New Zealand would probably struggle with 50 ICU cases in winter, particularly if we were dealing with the flu at the same time. Would we accept this future?

And finally…

At about 2.15pm on Tuesday, I was interviewing Fisher about New Zealand’s Covid-19 response. Work on this piece started last week, well before this week’s outbreak.

“I don’t think it’s a realistic ambition to stay at Zero (Covid) while easing measures,” he told me. “I don’t know what ‘stamp it out’ means. It’s not going to go away. While it’s in the world and transmissible through vaccinated people, the only way you can stamp it out and keep at zero is what New Zealand’s doing now.”

As we were talking about where New Zealand would be if only 50-60 per cent of the country were vaccinated (we’d have no choice but to continue with restrictive measures, he says), an email arrived.

The first line read: “A positive case of Covid-19 has been identified in the community early this afternoon and is now under investigation.”