As a surge in COVID-19 cases hits the population, a top epidemiologist says we're "flying blind" on the true extent of infection because there are "huge gaps" in our surveillance.
There were 9307 new community cases reported on Saturday and sadly, another 22 deaths, which takes the country's total death toll for the entire pandemic to 1663.
But Professor Michael Baker says we actually "don't know" how many people have COVID-19 because we're not doing regular community sampling, nor are we investigating people's immunity levels, as other countries like the UK are doing.
New figures obtained by Newshub show when our borders first opened, only 1.5 percent of international arrivals had their positive tests sequenced to monitor what variants were coming into the country.
The school holidays are here - thousands are flying out, and thousands are flying in.
Coming in too are COVID-infected travellers, but the actual prevalence of infection in New Zealand right now isn't known.
"We're basically flying blind in terms of the level of infection and the level of immunity in New Zealand," Professor Baker said.
We have the daily case numbers - but Prof Baker said that is not a true reflection of the situation.
"We've got big gaps in our surveillance knowledge. We don't know the level of infection in the community, we don't know much about immunity," he told Newshub.
And that has left Prof Baker disappointed as an epidemiologist.
"Well, I think we should all be disappointed because it means that we can't inform our decisions with essential scientific knowledge," he said.
To get a real understanding of COVID-19, Prof Baker said we need regular infection surveys - when you test different groups and different regions, even different schools, at regular intervals to get more reliable and real-time data.
He also wants serology - or blood testing - to detect immunity and better research about compliance with mask use and isolation rules to see how it relates to infection levels.
"This is one of the most basic tools - an infection prevalence survey and we really need it now, we really needed it yesterday," he told Newshub.
At the moment, the Ministry of Health's data relies on people to report positive rapid antigen tests (RATs).
But many aren't bothering, with Prof Baker estimating it's likely we have 50 percent more daily cases than the Ministry's figures show.
Another area our surveillance has fallen short is at our borders.
When they first opened in late February, Prime Minister Jacinda Ardern said all positive RATS should be followed up by a PCR, so they can know what and when new variants enter the country.
"Positive RATs must be registered and followed up with a PCR test," Ardern said on February 28.
But new figures show that genome sequencing was slow to start. Between late February and late March, 1166 arrivals tested positive, but only 18 - that's just 1.5 percent - got sequenced.
The following month - just over 2500 tested positive. But only 311 - that's 12 percent - were sequenced.
"We didn't have all the data we needed to say what was coming across the border," Dr David Welch, a senior lecturer at the Centre for Computational Evolution at Auckland University, told Newshub.
"We didn't have high confidence about what was arriving at the border at that time."
Since then, it has improved with between 20 to 40 percent of those landing who test positive using a RAT then getting a PCR for sequencing.
"It's a pretty good sample and it gives us a good overview of what's arriving," Dr Welch said.
"I think we could do a little bit better. I think we could make it easier for people to get that PCR."
An example is to give people an at-home PCR kit on arrival at the airport.
Alternatively, Rako Science director Leon Grice said it has saliva testing sites already running at the airports.
"There's no reason why we couldn't be doing PCR at the airport right now," he told Newshub.
"That would give you a bigger sample base to find out how many people who are positive are coming across the border, and also give you the samples to do the genotyping of what variants are coming in."
For Grice, Dr Welch and Dr Baker, our surveillance could be much better because, we need to know when new, more dangerous variants are arriving with accuracy and to know what's happening with infection in different communities.
It's two surveillance tools they say will lessen the impact of this second wave.
