New Zealand has reported more than 2.1 million Covid-19 cases since the pandemic began - including nearly 130,000 reinfections. Experts say 2023 will tell us more about what our long-term future with the virus looks like. Photo / Supplied
Experts say we’re about to get a clearer picture of what living with Covid-19 really means over the long term. Science reporter Jamie Morton looks at the three biggest questions before us in 2023.
When Omicron arrived around this time last year, and began washing through a population with little natural exposure to Covid-19, the result was always going to be an avalanche of cases.
That giant surge, which pushed daily numbers to nearly 25,000 at one point, proved twice the size of the winter wave that followed four months later.
Then came our similar-sized Christmas bump, powered not by one or two Omicron subvariants as before, but a “soup” of new types that caused thousands of reinfections – many of them amid Kiwis with waned immunity.
“Now, we’ve got an indication of what living with Covid-19 looks like – and in many ways, that’s the second and third wave we’ve just seen,” Professor Michael Baker said.
The Otago University epidemiologist has often pointed to the three intertwined variables that dictated our relationship with the virus: its evolution, our immunity against it and our social behaviour.
“It’s the classic triad of organism, host, and environment.”
With widespread roll-backs of public health measures and fewer Kiwis taking precautions, Baker said we’d effectively been left with two of those drivers – meaning things now hinged on shifts in the virus itself and our own changing immunity.
“Those two factors together are likely to create an ongoing pattern of waves – and the hope is that the intensity of these waves decreases over time.”
Covid-19 modeller Professor Michael Plank said waves appeared to be growing smaller as the pool of susceptible people shrank over time, with perhaps just a quarter of Kiwis still uninfected.
“2022 was the year when the vast majority of us were infected for the first time, and 2023 is going to look a bit different as that’s no longer the case.”
While susceptible people would continually be added to the population – namely with children being born – Plank said the virus would have to keep spreading through reinfections, which would “attenuate” the size of future waves.
It wasn’t yet clear how frequently surges would occur, or if we’d see as many in 2023 as we did last year.
“We’ve seeing them every three to four months, which is much more frequent than influenza,” Plank said.
“I think it’s possible that we’ll settle into a seasonal pattern, as we have with influenza, but it could take a while for that to happen – and it may be that we continue to get multiple waves each year.”
Another open question was whether the virus would stay on its current evolutionary path of producing tricky new subvariants in the ever-expanding Omicron family, such as the highly-competitive XBB.1.5, or “Kraken”.
A much more serious development would be an entirely new variant emerging – just as Omicron and Delta before it did – and driving a raft of new infections, hospitalisations and deaths.
Baker expected this year would also tell us much more about what burden Long Covid – a constellation of lingering symptoms thought to accompany perhaps one in 10 infections – will create over time.
Experts have warned the condition, shown to affect nearly every organ system in our bodies, with no treatment or cure in sight, could cast a decades-long shadow beyond the pandemic.
“This could add to the thousands of New Zealanders already living with the still poorly understood chronic fatigue syndrome or myalgic encephalomyelitis following other viral infections,” Baker said.
Countries that have been grappling with endemic Covid-19 since the start of the crisis have reported troubling statistics.
One December study estimated more than seven per cent of people infected in the US had persistent symptoms, with rates of 29 and 25 per cent in India and Denmark respectively.
“Some people may get a couple of Covid infections each year, which is very different from influenza where people usually go years between infections – so I’m very concerned about the impact this might bring,” Baker said.
“Will reinfection, over time, raise the risk for people? That’s a huge unanswered question and I think the jury is still out.”
Baker said others in the scientific community expected there’d be a diminishing impact from Covid-19 over time.
But already, there was plenty of evidence to suggest any reinfection could be risky.
One US study found that, compared to those with a first infection, reinfected people had at least one condition linked with Long Covid that still lingered on even six months afterwards.
Another bout could add to the woes of people already battling long-term symptoms.
In another recent global study, researchers surveyed hundreds of people who’d developed Long Covid, most of them after their first infection.
Among those still suffering lingering problems at the time they were reinfected, about 80 per cent saw their symptoms worsen, with a similar proportion reporting new or resurgent ones.
Of about 60 per cent who were recovering from the condition, reinfection was enough to cause a recurrence.
While reinfections in most healthy people typically came with reduced severity, Baker said having Covid-19 in our community meant ongoing deaths and hospitalisations were inevitable – even if these fell to a lower rate.
“Once something moves from being only an acute risk to also being a long-term condition, then other metrics come into play and we begin to weigh up years of life lost from both premature death and years lived with disability,” Baker said.
“Its possible that the greatest impact of Covid-19 may be through disability.”
And with the health toll came the economic one.
In the US, Harvard University researchers calculate the economic blow at US$3.7 trillion ($5.7 trillion).
In the UK, long Covid has been estimated to cost workers £1.5 billion ($2.8b) each month in lost earnings, with some two million sufferers reported as at mid-2022.
Across the Tasman, where up to half a million Australians may already be dealing with ongoing symptoms, economic forecasts have been put at an equivalent A$3.6b ($3.8b) in lost output.
We’ll also soon learn how the Government plans to continue using the most effective tool we have against Covid-19: vaccination.
Plank, who estimated that at least half the population had their last vaccine dose or infection more than six months ago, said New Zealand had at least two routes available to boost our immunity with it.
One was to continue efforts to reach those currently eligible for a vaccine dose, especially groups where risk is high or uptake was low.
“These include Māori and Pacific peoples, and the elderly. More than half of over-50s are still due for either their first or second booster,” Plank said.
“Using vaccination to top up immunity levels among older adults aged 50-plus will go a long way to reducing the health burden of Covid-19.”
The other was with Pfizer’s “bivalent” booster, targeting the BA.5 subvariant, expected to be rolled out in New Zealand ahead of the winter season.
“Although the virus continues to evolve its ever-growing family tree, using Omicron-based vaccines will provide a better match to currently-circulating variants, which are all part of the Omicron family,” Plank said.
“They may also broaden our immune response, meaning our immune system is less likely to be blindsided by a future new variant.”
In England, which began offering bivalent vaccines to over-50s in September, the new shots had been shown to halve the risk of hospitalisation compared with people whose last dose was more than six months before.
Here, it was unclear who exactly would be eligible for it – but further boosters had generally been limited to people at higher risk, the elderly or those with other health problems.
Immunisation Advisory Centre director Professor Nikki Turner said that, for healthy adults, two vaccine doses plus one booster still offered important immunity against Omicron.
“Having mixed immunity is good too, that is, for people who have had vaccinations and then also had Covid infection,” she said.
“Even if it’s many months from the first booster shot, for most people protection from severe disease continues.”
Beyond vaccination, Baker still saw room for further measures – including the return of masks to classrooms and on public transport if a severe wave happened to strike this winter.
Endemic Covid-19 also raised the need for indoor ventilation standards – along with CO2 monitors visible in busy public places like bars and restaurants – and smarter surveillance.
A regular infection prevalence survey still wasn’t in place, despite the Government originally planning to launch one after the first Omicron wave.
“If we’re transitioning to living with this virus, we need comprehensive surveillance on the rates of infection, symptomatic illness, and health impact in the community, including long Covid.
“We also need to track key interventions such as boosters, antivirals, testing, self-isolation and use of masks in high-risk environments. Such information is needed to guide the use and targeting of these important control measures,” Baker said.
“That’s why we urgently need this survey up and running this year.”
This summer will be critical to discover if the sharks have started returning.