NZ's 1400 Covid-linked deaths likely a 'conservative' count - expert

More than 900 people have died from Covid-19 in New Zealand - while nearly 500 have died with the virus being listed as a contributing cause. Photo / Getty Images

New Zealand's nearly 1400 virus-attributed deaths is likely still a "conservative" measure of how Covid-19 is driving up our mortality rates, an epidemiologist says.

Otago University's Professor Michael Baker also says that if our country continued to see high numbers of people dying with the virus, the toll could reach several thousand deaths in a year – potentially adding 10 per cent to the annual mortality rate.

"That would be 10 times the road toll. So, by every indicator, this is becoming one of the most common causes of death in New Zealand."

Earlier today, the Ministry of Health published updated information revealing more than 900 people had died directly from Covid-19 in this pandemic - and that the virus had been a contributing factor in nearly 500 other deaths.

The new figures showed 1396 deaths recorded since the start of the pandemic are formally Covid-linked – with 903 listed as the virus being the underlying cause, and 493 of it being "contributory" to the death.

All but 35 of those deaths occurred within 28 days of the person testing positive.

Of the remainder of the 2039 virus-related deaths reported since the start of the pandemic, 410 weren't linked to Covid-19, and there wasn't enough information to establish the virus' part in 233 deaths.

Source / Ministry of Health

Previously, the ministry had been recording virus-linked mortalities as anyone who'd died with 28 days of returning a positive test result.

Because it might have captured recently-infected people who'd died in unrelated circumstances, such as a car crash, this method of counting, though used elsewhere, has drawn criticism.

But the updated statistics – now being reported to the World Health Organisation - confirmed the majority of those virus-linked deaths reported each day were in fact tied to Covid-19.

Baker said the ministry's updated reporting was an "important refinement" - but the figures nonetheless painted a grim picture.

Over the past seven days, there'd been a daily average of 17 deaths confirmed as being attributable to Covid-19 - and 38 new virus-linked deaths were reported today.

"I find it very concerning that the moving average has not dropped below 10 per day, since fairly early on in our first Omicron wave," he said.

"Recently, it's been higher than any point during the pandemic. But even if we have 10 per day, that's still around 3500 deaths in a year, which would add 10 per cent to our annual mortality rate.

"This is going to have a measurable impact on life expectancy in New Zealand – and this burden won't fall equally across society.

"We know the rate of hospitalisation among Māori and Pasifika for serious infectious disease is two to three times higher in non-epidemic times – so we're probably going to see those inequalities reproduce yet again."

So far, Ministry of Health data shows Māori and Pacific people have accounted for more than a third of hospitalisations with Covid-19 – and nearly two in 10 deaths where the virus was the underlying cause.

Another major risk factor in hospitalisation and deaths was age: all but 44 of the 903 people who'd died from the virus were older than 60 - and two thirds of deaths were recorded among people older than 80.

Professor Michael Plank, of Covid-19 Modelling Aotearoa, said higher current death rates reflected the fact that more older people were being infected in this Omicron wave than our first one.

"We could continue to see those relatively high numbers for some time," he said.

"Hopefully, it will, it will drop off as the wave recedes. But as we know, deaths tend to lag behind cases – by several weeks, in some cases."

Baker was however concerned that our official mortality count represented just a proportion of deaths that stemmed from the virus in some form.

"The counter-factual question is, how many people might otherwise have survived another year?

"In general terms, we might say those who died directly of Covid-19, and those with other morbidities whose deaths Covid-19 contributed to, might have survived this year, in the absence of the pandemic.

"But we should also remember there will be people dying from conditions which are not attributed to Covid-19, but are actually caused by it."

Baker pointed out that just 5 per cent of influenza-linked deaths were actually coded as having been caused by that virus.

"The other 95 per cent die from conditions like respiratory failure, heart attacks and stroke – it's just they weren't tested for influenza before they died," he said.

"By every indicator, this is becoming one of the most common causes of death in New Zealand," Otago University epidemiologist Professor Michael Baker says. Photo / Supplied

"And often, they're in that similar older age group to people who are dying of Covid-19. Because many people dying won't have been tested for Covid-19 first, I'd consider the [ministry's counting] to still be a very conservative estimate."

Our excess mortality rate might give a more accurate picture of Covid-19's impact here, as it has in other countries, he said.

Still, the ministry considered its new reporting as a "more meaningful" measure in understanding the burden of severe disease from Covid-19.

"Over time that will also allow us to provide more and better demographic information about the people who have died from Covid-19 over the course of the pandemic such as by age, ethnicity, and by vaccination status," the Public Health Agency's deputy director-general Dr Andrew Old said.

Director-general of health Dr Ashley Bloomfield added the ministry now had systems in place to code deaths within a few days, rather than one or two or three months.

Old said the proportion of Covid-attributed mortalities might rise over time as more Covid-19 deaths were assessed and classified.

"It's important to note that this updated approach is consistent with the approaches taken in the United Kingdom, Australia and the United States ... and therefore more accurately reflects the contribution of Covid-19 to death numbers and overall rates."

Old also pointed out New Zealand had a lower cumulative Covid-19 mortality rate – currently 378 per million population - than many other countries, due to its successes early on in the pandemic.

By comparison, the UK's current cumulative death rate was 2718 deaths per million population, while in the US, that rate was 3047 deaths per million population.