As the latest Covid wave plateaus, New Zealanders may well be wondering when this whole sorry mess will end. Keith Lynch explains the arms race that New Zealand (and the rest of the world) now face.
Recently Professor Philip Hill, a prominent epidemiologist who has advised the government throughout the pandemic, quietly urged health officials to keep an eye on South Africa for a sense of what could come next.
South Africa has had five distinct Covid waves since 2021, the latest powered by the BA.5 variant. What South Africa has also seen is a clear decoupling of Covid cases and deaths.
The reason being, Tulio de Oliveira, the lead of the Network for Genomic Surveillance in South Africa, recently told The Guardian, was hybrid immunity – a combination of vaccination and previous infections.
* Covid-19 NZ: Why the rising tide of cases doesn’t tell the whole story
* Omicron NZ: Why the government is doing (almost) nothing about Covid
* Covid-19 NZ: Understanding the Omicron variant BA.5 and why it’s fuelling a second wave
In other words through great costs (including thousands of deaths) South Africa has forged a wall of immunity that is broadly protective against the worst Covid can throw at it.
To be clear New Zealand is not South Africa, as Hill outlines. Our own immunity wall has a distinctive flavour seasoned by mass vaccination and relatively recent Covid spread. And our population is older.
So while the BA.5 wave in South Africa was much less impactful than earlier deluges, that hasn’t been the case here. This isn’t necessarily just a product of the virus, it’s also a product of the immunity the virus is facing up to.
We know far more elderly people, who evaded the March onslaught, have been infected recently.
What makes South Africa so interesting, though, is that waves have become progressively less awful.
In a way, this echoes the pandemic of 1918 when a new strain of influenza emerged in Spain. Over the coming years, it hit in waves killing tens of millions of people worldwide.
Reports from the time, as in The Washington Post, suggest the virus became less lethal as time passed.
But the flu didn’t just pack up and go home. It continued to do the rounds and even today descendants of that flu virus unleash illness and death – just not to the same extent.
What happened is our immune system grew accustomed to it, making its annual appearance certainly troublesome, but both manageable and acceptable.
‘Manageable and acceptable’ – these two words sum up Aotearoa’s (and much of the world’s) current approach to Covid.
The world’s acceptance of Covid spread is also, in part, seemingly fuelled by the basics of immunology: as our immunity compounds and broadens, we should see fewer of the worst Covid outcomes.
There are clearly risks with this approach. There are no guarantees that Covid mirrors flu (which still kills a lot of people every year). Amid so many chances to mutate, a more virulent variant may well emerge over time (yet even that would likely be hamstrung by the world’s three-year-old immunity). Covid is certainly not harmless and mass infection yields mass illness.
There’s an inescapable reality, though: this is where we are at. While New Zealand isn’t necessarily embracing widespread infection, it has, by and large, accepted it so we need to understand what that means.
What we’re now confronted with is a cat and mouse game. On one hand there’s our growing wall of immunity but on the other, there’s the virus itself pushing back, shifting, morphing and evolving to do the only thing it wants to: mindlessly reproduce as efficiently as it can. It is not going away.
It’s these dual conflicting forces that will define what comes next.
What’s this immunity wall?
Both the vaccines and a Covid infection stimulate our immune systems, creating antibodies.
These are basically your first line of defence, ready to roll at the first sign of infection.
Over time these antibodies dissipate or wane, meaning we’re more susceptible to catching the virus.
This really shouldn’t have been a surprise. A 2020 study found that the four other circulating coronaviruses (that cause common colds) could quite easily reinfect people annually.
“Essentially immunity to mucosal infections (like Covid) will always wane quite quickly and even if it didn’t, new escape variants will appear (probably forever) so infections will always keep happening,” Paul Hunter, professor in medicine at the University of East Anglia and an expert in infectious diseases, says.
Thankfully, our immune system is much more than easily distracted antibodies.
The immunity brought on by the vaccines, as one recent study explains, is based on the existence of what’s called immunological memory: that is, the immune system can remember how to fight back against pathogens like Covid-19.
This is immunology 101, Dr Nikki Moreland, an associate professor in infection and immunity at the University of Auckland, tells me. And it will ultimately help define our Covid future.
In a nutshell the vaccines (and infection) also bring about more enduring soldiers called B and T cells, which kick into action when needed to stop severe illness.
So while the virus has become more skilled at dodging our antibodies it has not yet (and probably will not) entirely sidestep our immune response.
Immunity against severe disease, Hunter says, “is more robust, lasts longer and, so far, transfers to new variants. That is because immunity to severe disease is associated with different aspects of the immune system (those B and T cells) that have a longer half-life”.
This more durable response – brought on mostly by vaccination in New Zealand, but now propped up by infections – is the cornerstone of the immunity wall that makes the spread of the virus somewhat acceptable in 2022. Such spread in 2020 would have been catastrophic.
You can see how this has played out in the numbers.
So far, there have been 1250 or so Covid deaths (caused by the virus or where it was a contributing factor) from approximately 1.5m confirmed, mostly recent, cases – a case fatality rate of approx eight deaths for every 10,000 cases (0.08%).
(The true risk of death is lower because far more than 1.5m people have been infected.)
To give you some context, some case fatality rate estimates for the original strain, which scientists believe had similar severity to Omicron, veered close to 1 death for every 100 cases.
But we’re going to be reinfected a lot, aren’t we?
The science around reinfection frequency and severity is somewhat uncertain. What we’ve seen in the UK, for instance, is that even BA.5 is still disproportionately hitting those who have so far evaded Covid-19.
In recent weeks viral claims suggesting a default of constant Omicron reinfections – every two to three weeks – have done the rounds. But these claims are just not realistic. Just because reinfection is possible within a month or so doesn’t make it universally inevitable.
Recent data suggests that a BA.2 infection does offer decent (but not total protection) against BA.5 reinfection.
New figures from Denmark also suggests a previous Omicron infection offered significant protection against BA.5 reinfection in vaccinated people.
What about how severe they are?
Two studies have attracted quite a bit of attention in recent weeks – one from Qatar, which followed unvaccinated individuals, infected pre-Omicron, who were then re-infected either pre- or post-Omicron.
It found a pre-Omicron infection brought on almost total protection against severe illness following a reinfection. This may not be that much of a surprise given those in the study were mostly young.
Another (very controversial) US study looked at a much older group, with a median age of 60, a lot of whom were quite unhealthy. Now this study did not seek to determine if the second infection was worse, but only if those who suffered a second infection had worse health outcomes than those who did not.
It found, in that particular group, that getting reinfected was worse than not being reinfected.
“So, in this case at least, re-infections were not ‘mild,” Australian based professor Michael Fuhrer tells me, “but again, this was a group in which initial infections were also not ‘mild’; 20% were hospitalised.”
His reading of the situation is as follows: “Young, healthy people will very likely experience re-infections as ‘mild’. For older and/or unhealthy groups, any infection could be significant. This isn’t too surprising: the vast majority of influenza deaths are due to reinfections (elderly people who have had influenza sometime in their lifetime).”
The consensus of those I spoke to for this piece was: repeat infections, generally speaking, will not be as severe as first go around – which is supported by a range of studies.
Keep in mind, though, we’re still learning about the cumulative impact of infections on longer-term Covid outcomes.
So everything is OK then?
No. Even though the virus poses less of a risk to individuals than it once did, one unavoidable dilemma remains: scale.
This is the classic a “small percentage of a big number is still a big number” problem.
Sure, Omicron isn’t that likely to kill the average person. But if a million people end up infected all at once, quite a few – particularly older folks – get dealt a bad hand.
Covid has killed more than 1000 people in New Zealand and while the death rate may well fall, the virus will still regularly kill people and put major strain on health services.
Trevor Bedford, a US computational virologist, believes, for example, Covid could still kill 100,000 Americans every year.
Much of this comes down to how elderly people, in particular, struggle to build immunity to new pathogens.
While most people will be protected by their own personal immunity bulwark, not everyone will. As The New York Times gloomily puts it: “If the rest of the world is now building a higher and higher immunity wall, with each additional booster or infection adding some amount of protection – and future variant-specific boosters or pan-coronavirus vaccines potentially adding even more – the vulnerable old are building their own walls a bit more slowly and fitfully.”
Essentially this may well mean the virus remains pretty ‘novel’ for a lot of New Zealanders, meaning things won’t necessarily settle down any time soon.
The hope is as immunity builds the maths falls even more in our favour – that is the average person’s chance of awful Covid outcomes falls off even further, making the virus’ spread across a population more acceptable and manageable.
Ultimately, this is the 2022 Covid Catch-22. Yes, of course infection is crummy and should be avoided. As a number of public health professionals will point out, severe illness and death are not the only metric of concern.
What’s more, widespread Covid-19 spread also gives the virus more chances to mutate and sidestep our immunity wall.
But at the same time infection – which is happening whether we like it or not – is not meaningless.
Oh yeah, tell me about what the virus is doing
Covid-19, like all viruses, just wants to make more of itself as efficiently as possible.
As The Atlantic reports, Covid’s first “need was speed”, to infect as many people as possible as quickly as possible.
Along came Alpha, followed by the increasingly nasty Delta variant. But speed would only take Covid so far. The immunity brought on by vaccination and infection was hampering its spread.
Then came Omicron, a dynasty (BA.1, BA.2, BA.2.12.1 BA.4, BA.5, BA.2.75) particularly adept at evading immunity.
The immunity wall I’ve outlined above essentially boxed it into a corner. It’s fighting back and will continue to.
Virologist Dr Jemma Geoghegan’s view is that the virus could still throw up even more dramatic surprises. Essentially the route the virus has taken is just one of many evolutionary paths, but that’s not to say “there are not entirely different avenues the virus can go down”.
It won’t necessarily hit some sort of evolutionary ceiling anytime soon, she says.
“It’s a constant arms race between the virus and the host. Our immunity is always adapting to overcome the virus and the virus is always adapting to try and overcome that immunity. And that will always happen.”
Let me use a scenario to flesh out what this means in real life.
Assume for a moment that BA.2, which drove our first main wave, remained the undisputed Covid king and let’s assume that once a person went through an infection they had almost total protection against reinfection for a year or so.
If this had been the case, the Covid waves would have been somewhat predictable, predicated by our antibodies waning, not by the virus’ weird and constant shifts.
But in real life along came BA.5, and while early data suggests that yes, your BA.2 infection should hold up ‘fairly well’ against reinfection (about 75% or so according to one of the studies flagged above) that protection is still fairly leaky.
As Professor Michael Plank puts it: “the flip side of 75% immunity (to infection) is 25% susceptibility”.
It’s almost certain other iterations of Covid-19 are around the corner, borne out of a necessity to evade the protection its younger siblings left us with. What if we’re 30 or 40 per cent susceptible to reinfection next time around?
There is good news though. The virus hasn’t entirely swerved our immune system, particularly those barricades against severe illness.
“The virus is moving to where it can go, and what’s surprising is the speed at which it’s doing that. But even still it’s not moving completely beyond our immune memory or that collective immunity wall,” Moreland says.
There’s also no guarantee that the virus will become less severe over time. Omicron’s retreat from the Delta’s deadliness was pure chance. We may not necessarily get as lucky next time around.
But will the disease therefore become more regular or predictable? Opinions are mixed. Some of those I spoke to for this piece expect seasonal Covid. Others, not so much.
It may be, as Dr Stephen Kissler, an infectious disease expert from Harvard University says, that Covid finds it easier to spread in winter. But there’s no reason, given its evolution towards ‘shockingly infectious’, that it won’t just surge in the colder months.
”If you take a step back, I think we’ll see higher rates of spread in winter and lower spread in summer but within that I think it’ll be fairly chaotic and jagged. We’ll see this ebb and flow of cases as new variants emerge.”
There are encouraging signs that this current wave has reached a lower peak than expected. This may be because of behaviour, or it may be we overestimated how good BA.5 is at dodging pre-existing immunity.
It may now be possible, Plank says, that we see a lower baseline of cases, hospitalisations and deaths simply because there are fewer people out there that haven’t been infected.
In the short-term at least. We’ll see.
As our antibodies wane new surges may well occur. Another iteration of Omicron, better able to evade the immune brought on by BA.2 and BA.5 could well come along in the coming months. A number of virologists remain concerned about a subvariant called BA.2.75.
It may be a totally left-field more transmissible and more severe variant is thrown off, upending the pandemic’s trajectory.
There are no guarantees.
New vaccines – targeting specific variants – would clearly help, allowing us to top up and improve the immunity wall without the pain of infection – although there are questions whether they’ll keep pace with new iterations of the virus.
Hunter’s view of the long-term is this: “Each wave will generally (but not inevitably) be associated with less severe disease and fewer deaths even if infection numbers are still very high.”
Moerland agrees: “I do think that in every wave, we should see proportionally less severe outcomes, because we’re just building more and more hybrid immunity in the population.”
The timings and severity of those waves will very much depend on how ‘fresh’ or good our immunity and Covid’s next flavour.
Looking further forward, Kissler is optimistic, hopeful that as we learn more about the virus and how to neuter it, things improve.
But these next few years? Not so much.
“I think the situation that we’re in is that we have an incredibly creative and infectious virus that’s spreading all over the world. And we have a population that has really lost an appetite, and reasonably so, to do much to deal with it.
”And that’s going to continue to take a toll.”