New Zealand's death toll from Covid-19 could fall lower than that from seasonal flu - or it could soar in the thousands - depending on how high the country can lift its vaccination rate.
A new modelling report has indicated it's possible to vaccinate 90 per cent of the population against Covid-19 - something that could even spare more than a million infections and largely free Kiwis from constant lockdowns.
But the modelling, just released by Te Pūnaha Matatini researchers, also suggests that vaccinations alone won't be enough to keep the virus at bay and public health measures would still be needed.
With the Pfizer vaccine expected to be approved soon for use in children aged 5 to 11, the modelling found this could lift coverage as high as 90 per cent – the threshold at the centre of a new Herald campaign.
It painted a much more optimistic picture than earlier modelling by the same researchers, which found 97 per cent of Kiwis would need both Pfizer jabs for New Zealand to withstand Delta without the need for harder measures like lockdown.
But that was before the vaccine became available to young people over 12 – and before it could be assumed the shot would be approved for children older than 5 years old.
The modelling, however, still came with troubling figures around what could happen if vaccine uptake – around 40 per cent of eligible people have so far received both doses, and 35 per cent one dose only – fell lower than 90 per cent.
Even at 80 per cent coverage of over 5s, and assuming only baseline public health measures and limited test-trace-isolate-quarantine, the modelling carried a median estimate of 1.1 million infections, around 60,000 hospitalisations and nearly 7000 deaths – all within just a year.
At 70 per cent coverage, the corrresponding figures were 1.7 million infections, around 110,000 hospitalisations, more than 13,000 deaths, and nearly 18,000 hospital beds occupied at the peak.
At 90 per cent, however, the modelling pointed to 171,000 infections – but only around 6000 hospitalisations, just over 600 deaths, and 438 beds occupied.
When considering uptake among over-12s only – but with the rest of the same modelling assumptions and time period – the figures indicated that, with just 70 per cent coverage, there could be more than two million infections, 120,000 hospitalisations, 15,500 deaths and more than 21,000 hospital beds used at peak.
That compared with around 970,000 infections, nearly 30,000 hospitalisations around 3,500 deaths at 90 per cent – but 1.5 million infections, 71,000 hospitalisations and nearly 9000 deaths at 80 per cent.
The picture changed again when the modellers assumed that full test-trace-isolate-quarantine measures were possible, along with baseline public health measures.
In this case, median estimates showed that vaccinating 90 per cent of over 5s could keep infection totals as low as around 13,000 – with around 470 hospitalisations and just 50 deaths.
But even with that extra protection, vaccinating 90 per cent of only the over-12 population could still mean 460,000 infections, nearly 14,000 hospitalisations and more than 1500 deaths.
"The modelling results show the importance of New Zealanders achieving the highest vaccination coverage we possibly can," modeller Dr Rachelle Binny said.
"If nearly every New Zealander gets the vaccine, we could avoid the need for strict alert level 3-4 restrictions."
At the same time, the increased threat posed by the Delta variant has become clearer with recent data showing it is more infectious and more likely to cause severe illness.
"The modelling tells us that for Delta, population immunity is still out of reach by vaccination alone," Hendy said.
In an 80 per cent scenario, higher alert levels would still be needed to control transmission – but that need was reduced with higher coverage rates.
"If we can get vaccination rates well over 90 per cent of over 12s or into the 5-11 age group, then the virus can be controlled with more sustainable public health measures," modeller Professor Michael Plank said.
"Testing, contact tracing and wearing face masks will lead to considerably better health outcomes."
Binny described the alternative as "bleak".
"Failing to reach these high levels of vaccination would mean we will need to keep relying on lockdowns and tight border restrictions to avoid thousands of fatalities," she said.
"This could cripple our healthcare system, and Māori and Pacific communities would bear the brunt of this health burden."
The model provided a rough guide to the benefits of high vaccination rates at the population level, not a detailed roadmap for reopening.
The results ultimately showed that, if we want to see an end to lockdowns, we need to strive for very high vaccine coverage.
It also showed how essential it was to achieve high vaccination rates not just nationally, but also in specific communities including Māori and Pasifika populations.
"The results here demonstrate the considerable benefits of achieving high vaccination coverage in the coming months," Hendy said.
"The message from the modelling is that Covid-19 is going to continue to disrupt our lives for some time yet, but that we can minimise that disruption by ensuring we all get vaccinated.
"There is no magic threshold for vaccination coverage. But the higher the coverage, the fewer restrictions we will need in coming years.
"And most importantly, we need every community to be well covered by vaccination. We can't afford to leave anyone behind."
Over the coming weeks and months, the modellers expected to release a more detailed look at what measures might work best in the community and at the border.
Survey statistics have generally put New Zealand's potential uptake among the eligible adult population at around 80 per cent.
The most recent survey commissioned by the Ministry of Health, as at June, found that 19 per cent of those not already vaccinated said they were unlikely to have a vaccine – a rate that would proportionately increase as the drive wound on.
Those aged between 24 and 34 years were the least likely to get a vaccine – and the main reasons cited among people unsure or unlikely to receive the jab were feeling they didn't need to, concerns about safety, or waiting to see if others had side-effects.
GP and health researcher Dr Rawiri Jansen said he agreed very high vaccination rates were required to avoid significant hospitalisations and deaths.
"Very high vaccination rates are achievable – evidenced by some providers achieving childhood immunisations rates higher than 90 per cent," he said.
"This likely requires of us - health system and health providers - to be deliberate, dedicated and relentless. The benefits to our communities and Aotearoa are obvious."
University of Auckland infectious diseases expert Associate Professor Siouxsie Wiles said the new modelling supported what was being seen overseas – that high vaccination rates, including in younger children, were needed to keep hospitals from being overwhelmed by people suffering from Covid-19.
"It has been distressing to see the reports of paediatric intensive care units in the US filling with sick children because they cannot yet be vaccinated."
Wiles pointed out that the good news was that vaccine trials in children were currently underway, and that there was no reason to suspect there wouldn't be a safe and effective vaccine available for children sometime next year.
"The data clearly shows that we will need everyone who can be vaccinated to be vaccinated if we want to manage the pandemic and any outbreaks without needing to use alert levels 3 and 4," she said.
"Yet we know that there people creating and sharing false and distressing misinformation about vaccines that is making people question whether they want to be vaccinated.
"The research shows that we are influenced most be people who we love and care for.
"That means all of us need to reach out to our families and friends, to show empathy and understanding of their distress, and to make sure they have access to the correct information about the safety and effectiveness of vaccines."