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• Covid-19 modellers say any summer surge will come with a smaller peak than 2022 and 2023.
• 2024 is likely to finish with around a quarter of the Covid-attributed deaths of 2022
• An epidemiologist told the Herald that number likely represents just a fraction of Covid-19’s real burden: there remain troubling unknowns about repeated exposure.

After New Zealand’s third year of living with Omicron, what have we learned about Covid-19? And what can we expect for 2025? Jamie Morton explains.

Will NZ get another summer Covid wave?

For too many of us, a Christmas bout of Covid-19 has become a trend about as welcome as a lump of coal.

And while case rates have been slowly ticking upward over recent weeks, hospitals and GPs aren’t seeing the same late-year surge they did in 2022 and 2023.

If another wave does kick off over summer – and Australia is right now observing early signs of a bump – modellers expect it to come with fewer infections and hospitalisations than previous spikes.

That would continue a pattern of six-monthly Covid-19 waves that have become smaller over time, as our immunity landscape has grown ever-more complex.

The University of Canterbury’s Professor Michael Plank told the Herald that back in early 2022 Omicron spread “like wildfire” through a population that was well-vaccinated but had little exposure to the coronavirus itself.

“Now, most of the population has had Covid at least once or twice, which means we have broader immunity to a range of different variants,” he said.

“That makes it harder for the virus to spread – the fire hasn’t gone out and probably never will, but it’s more of a slow burn now.”

Because New Zealand doesn’t run a national infection prevalence survey, it’s hard to tell just how many Kiwis are catching the virus each year.

But wastewater surveillance data suggests levels of Covid-19 have been dramatically lower in 2024 than 2022, and hospitalisation rates have also gradually fallen.

The number of Covid-attributed deaths this year will likely finish up at around one-quarter of 2022’s 2800 deaths, becoming comparable with seasonal influenza mortality, Plank said.

“This doesn’t mean we can ignore it: both Covid and influenza impose a significant health burden, which falls disproportionately on some groups including Māori, Pacific People and people living with high levels of deprivation.”

The figure also likely represented just “a fraction” of the deaths that the coronavirus has contributed to, Otago University epidemiologist Professor Michael Baker said.

Baker said the lower number of deaths in 2024 might be partly because there were now fewer very vulnerable people in the population succumbing to the virus than three years ago.

“But it’s hard to speculate on what the cumulative effect of vaccination and exposure is.”

Similarly, he said it was tough to predict whether Covid-19 would continue its “slow burn” pattern of twice-yearly waves or settle into a seasonal regime like influenza.

Will the coronavirus shift again?

If you’ve caught Covid-19 in the past few weeks, the culprit has most likely been an Omicron sub-variant named KP.3.1.1 – an off-shoot of the JN.1 strain that fuelled last summer’s spike.

ESR’s genomics and bioinformatics science leader Dr David Winter said this accounted for around two-thirds of sampled cases from the past two weeks, while the more recently arrived XEC strain made up just under a quarter.

“This is similar to international trends.”

Since Omicron surfaced three years ago, it’s branched out into more than 300 separate lineages.

New Zealand has seen a succession of new Omicron variants over the past three years - with KP.3.1.1 making up the bulk of current cases. Image / ESR

And while they’ve packed mutations that help the virus to evade our immunity and spread faster, they’ve lacked the severity that made predecessors like Delta so deadly.

For virologists, the biggest question remains whether the virus will take another dramatic evolutionary leap, potentially up-ending much of the immunity we’ve built to it so far.

For now, Otago University’s Professor Jemma Geoghegan considers that unlikely.

“I think it will be more of the same, with the virus adapting to our immune system and vaccines,” she said.

“I can’t see how big shifts could happen without the introduction of new variants from another species.”

Will we solve the puzzle of Long Covid?

Another big unknown facing researchers is what’s causing the hidden health burden that is long Covid.

It’s a constellation of persisting symptoms and known to affect nearly every organ system in our bodies, with previously healthy sufferers telling of ruined lives and livelihoods.

Several cohort studies have suggested these lingering symptoms can accompany 4-14% of infections, while another analysis found it could be costing New Zealand around $2b in lost productivity – or around 0.5% of GDP.

Researchers last year launched a Long Covid Registry to build a clearer picture of its impact in New Zealand and recently made two dozen recommendations to better address the issue.

But advocates say there remains a woeful lack of Government support and action – New Zealand has just one Long Covid clinic, based in Taranaki – or research funding to unravel its mysterious causes.

“Although we know a great deal about what systems are impacted, we still don’t have good clinical tools for diagnosing, and no approved treatments,” University of Auckland immunologist Dr Anna Brooks said.

On top of that, she added, researchers still didn’t understand which groups were most at risk of developing Long Covid.

“Each infection is a roll of the dice: we need a better understanding of the impacts here in New Zealand, prevalence, including in Māori and Pacific populations, and importantly, developing a strategy to track and manage those that are impacted,” Brooks said.

“The virus is still circulating, it’s still causing harm, and it will continue to do so therefore investment in reducing harm, minimising new cases, and researching treatment options remains urgent.”

In face of these troubling unknowns, Baker said catching Covid certainly shouldn’t be framed as an immunity-boosting positive.

Otago University epidemiologist Professor Michael Baker.

He also argued vaccines should be made more widely available – and be promoted more actively.

“There’s no question now that vaccination reduces your risk of long Covid, but you need to keep getting revaccinated regularly.”

Plank agreed it’d be helpful to have a clearer vaccination strategy, guiding when we received vaccines, and when they were recommended for eligible groups.

“However, the biggest factor limiting the benefits of vaccination is that uptake is relatively low.”

For Kiwis anxious about catching Covid-19 this season, Plank suggested they book their booster now.

“Nobody wants to have Covid ruin their Christmas or summer holidays: and the best way to protect yourself is to go get that vaccine if you’re eligible.”

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.