Prominent epidemiologist Professor Michael Baker contradicts the Prime Minister over the spread of Omicron. David Williams reports
In mid-November, the race was on.
Most DHB areas were steaming towards the magic 90 percent figure for the double-vaccinated, as the country experienced record numbers of community cases of the Delta variant. Summer was approaching and many, especially those in Auckland, were restless.
Prime Minister Jacinda Ardern took the podium at the Beehive Theatrette on November 17 to announce the country was to move into the traffic light system. Also, Auckland’s border restrictions would be dismantled for vaccinated or tested people, from December 15 to January 17.
From that January date, can everyone go everywhere, the PM was asked, and can we go back to living our lives?
By then, Ardern said, vaccination levels will be even higher. “We will have used testing and vaccine certificates to really slow down any potential spread of Covid but we do also need to move into a phase where we don't have hard borders in New Zealand anymore.”
The arrival of the more infectious Omicron variant ruined dreams of an unfettered summer, of course, but it’s worth returning to mid-November because it marks a very different phase of the pandemic, and a different mindset.
Back then we were getting tested in big numbers.
In the 24 hours before Ardern’s traffic light announcement, when the country hit a new high of 222 cases, there were almost 33,000 tests.
Until Thursday’s uptick of more than 27,000 tests, the seven-day rolling average was a tick above 18,000 – barely more than the tests across the three Auckland DHBs in mid-November.
The exponential rise of the Omicron variant has changed things.
Cases on Thursday hit a new high of 306, and experts believe we could be just a fortnight away from 1000 cases a day, when the country would enter “phase two” of the Government’s pandemic plan.
Reasons posited for low testing numbers include complacency, and Covid fatigue. Reports in the deep south suggest farmers are demanding staff not get tested to avoid potential disruptions because of isolation rules.
But University of Otago epidemiologist Michael Baker is urging the public to continue to get tested if they have symptoms – and not to take Omicron lightly.
Excluding border restrictions – which will soon be scaled back – there are three main tools to slow the spread of Omicron in the “mitigation” strategy: vaccines, contact tracing, and transmission-limiting measures like masking, physical distancing and gathering restrictions.
If testing is too low the outbreak will accelerate more rapidly, Baker says, leading to more serious illness and deaths, and possibly overwhelming the stretched health system.
Another key metric to measure Omicron’s spread is the positivity rate – the number of positive cases as a proportion of tests.
On Tuesday, as double-vaccinated Kiwis were urged to get boosted, Ardern put a positive spin on falling testing rates by saying the positivity rate still sat at about 2 percent. “That suggests that we aren’t missing a large number of cases, but if you’re symptomatic, please do get a test.”
Baker’s take is markedly different.
Since Omicron was discovered in the community, the positivity rate has gone from 0.2 percent (two in a 1000), to a moving average of 1.66 percent – a more than eight-fold increase.
“That’s a huge increase in positivity,” Baker says.
“It’s telling us that we’re almost certainly missing a lot more positive cases now than we were. And it’s what we'd expect to see with the beginning of this really steep exponential rise. And there are a lot more infected people in the community then those numbers indicate at the moment.”
The Ministry of Health’s group manager of Covid-19 testing and supply Darryl Carpenter says testing rates understandably dipped during the Christmas/New Year period but he’s buoyed by the increase in tests processed on Wednesday. “This is what we want to see,” he says via an emailed statement. “It’s the best way to continue to detect Covid-19 in our community.”
Carpenter says the country’s test positivity rate, a key measure of the effectiveness of the testing system, “has consistently been among the lowest in the world”.
Baker says even those with mild symptoms have a social responsibility to get tested.
“If you’ve got this infection, you don’t want to be sharing it round. Particularly if you’re going off to work, you may have older people there, people with underlying illnesses, maybe visiting older relatives, or you may even just infect someone who takes it home to their family, and then someone may get seriously sick.”
‘Still inherently dangerous’
There’s an element of truth to the perception Omicron is less severe – for people who have been boosted, at least. But Baker warns it’s still dangerous.
Just look across the Tasman. In mid-January, Australia had more than 4000 cases per million people – well above the likes of the United States, United Kingdom, and Italy. Daily deaths peaked a few weeks later at 134 people, far higher than the initial wave in 2020.
Covid-related deaths in Australia have doubled since Christmas, to total more than 4400.
“Omicron is killing more people than ever, in some parts of the world, just because it's infecting so many people,” Baker says.
“This virus is inherently still very dangerous … it’s definitely less dangerous than the Delta variant but it is somewhat similar to the ancestral Wuhan virus that we encountered for the first year, which still killed millions of people.
“So while it’s relatively less severe than Delta – and also because we are highly vaccinated we have a lot more protection – it doesn't mean that people can ignore it.
“It’s still vital that people do get tested.”
(Ministry of Health manager Carpenter says there’ll be a rollout of rapid antigen tests “for all critical businesses in New Zealand”.)
With the positivity rate below 2 percent, the overwhelming majority of people who get a PCR test will get a negative result. That will be reassuring, Baker says, before he issues an ominous warming. Given the trajectory of Omicron, he says PCR testing is likely to get swamped in the next couple of months.
Even more incentive to get a test now, it seems.
