New Zealand's Covid-19 case numbers may yet keep falling further, a modeller says, even as daily counts drop to levels not seen since the start of our first Omicron wave.

After reaching nearly 12,000 amid the BA.5-driven winter wave, daily cases numbered just 1,296 cases today and 1103 yesterday.

There are 257 people in hospital and four people in ICU.

There are four deaths reported today linked to the virus.

The seven-day rolling average of hospitalisations is also down, sitting at 273 compared to 351 this time last week.

Today, the weekly rolling average of new infections is 1,778, down from 2,425 cases last Monday and continues a trend of falling below 2,000.

The bulk of the climb-down had occurred over August, when daily numbers fell from more than 7000 to fewer than 2300 by the month's end.

"They're still trending downward at the moment, at a rate of about 20 to 30 per cent per week - so there's not really a sign that they're levelling off into a plateau yet," said Professor Michael Plank of Covid-19 Modelling Aotearoa.

The biggest factor in the decline was likely that the virus was now finding fewer people to infect.

Last month, Plank said at least half of the population has now been infected – and those who hadn't yet had the virus were likely among a minority.

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"The proportion of infections that are reported is probably somewhere between 40 per cent and 65 per cent," Plank said at the time.

"It's unlikely to be much less than 40 per cent because at least 40 per cent of all 20 to 25 year olds have already reported a case."

On the other hand, he said, the reported infection rate was typically less than 65 per cent of the infection rate in routinely tested cohorts such as border workers.

"This means it's likely that at least half of New Zealanders have had Covid-19, although those that haven't probably still represent a significant minority."

Speaking to the Herald today, Plank said a potential drop-off in people getting tested might also be contributing to the falling figures.

"That's possibly happening to some extent," he said.

"But the fact that hospitalisations are also trending downward and falling at a similar rate, I think we can say this drop in cases is a real effect, rather than just a testing artifact."

Yesterday, another 11-virus linked deaths were also reported.

As at Monday morning, there had been 2845 virus-linked deaths, of which 1915 had been attributed to Covid-19 either as the underlying cause or a contributory factor.

This comes as Prime Minister Jacinda Ardern has announced that, after living with the traffic light system for nearly a year, it was time to look at whether current settings were still "fit for purpose".

The outcome of the latest review was expected to be announced next week.

Despite the lower case numbers, experts have urged the Government to keep in place core measures like masking in high-risk settings and mandatory isolation periods for infected people.