The trend of falling daily cases Covid-19 should be treated with caution, the Ministry of Health says.

There were 15,161 new community cases Sunday, more than 3500 fewer than Saturday's total of 18,833. On Friday, it was 22,527.

It is the third day running that case numbers have fallen.

Covid-19 Modelling Aotearoa project leader Dion O'Neale says the shift to Rapid Antigen Tests and focus on personal responsibility in reporting cases could be throwing numbers off.

He says the under-12 age group could account for a large gap, where self-reported cases must be done so over the phone, rather than through the online My Covid system.

Dion says it's also possible that Auckland might be close to reaching its peak, causing numbers to slow.

"It is really going to be peaks of different times in different regions,” he explains.

'So Auckland very much could be nearly there to see that signal of case numbers increasing slightly more slowly for a while."

He says it could be some time before cases peak in other regions.

Urging caution, the MOH says: "The variation in reporting numbers each day means that the rolling average of cases gives a more reliable indicator of testing trends. The seven-day rolling average of cases is today 17,272, up from 16,687 yesterday".

"Additionally, public health officials consider that one possible reason for the decrease in cases could be related to delays in people self-reporting Rapid Antigen Test results, even if it is a negative result.

"It is essential we have as much information as possible to inform public health decision-making. If you take a Rapid Antigen Test, report the result online through My Covid Record."

Instructions for self-reporting RAT results can be found on the Unite Against Covid website

RAT result reporting dropped from Thursday to Saturday - from 71,084 on Thursday, to 55,994 on Friday and 41,637 on Saturday, numbers provided to RNZ showed.

Those numbers included includes both self-reported RATs results from people uploading their results to their My Covid Record, and supervised results taken at a community testing centre or other healthcare setting.

The ministry says "as with testing numbers more generally, we would expect to see a drop in RATs results reported over the weekend".

Over the weekend, epidemiologist Professor Rod Jackson said people should not read too much into the decline in Covid-19 case numbers.

"I hear every day, and frequently every day, of people with symptoms not getting tested and of those with symptoms who do get tested not reporting them.

"I think a lot of people have given up reporting, so I take next to no notice of the cases anymore. I look at the hospitalisations and the deaths."

In yesterday's coronavirus update, the MOH said 618 people were in hospital, 10 were in intensive care and one more person had died - taking the total of Covid-19-related deaths to 65.

Hospitalisations were "significantly greater than those from last year's Delta outbreak", the ministry says.

"The hospitalisation figure of 544 on Thursday was six times the peak in hospitalisations seen in the Delta outbreak last year.

"The number of cases in hospital is currently expected to peak in the second half of this month.

"The Omicron variant means people who are hospitalised are more likely to have a shorter stay and less likely to be admitted to ICU or require oxygen or ventilation support."

- RNZ