One Covid-19 expert says he is not surprised by the rise in cases and believes it is now a race between the Delta outbreak and vaccination rates.

On Tuesday New Zealand recorded the largest number of new cases reported in one day since the start of the pandemic, with over half of the cases yet to be linked to the outbreak.

Ninety-four new Covid-19 cases were reported, 87 in Auckland and seven in Waikato. Six of the seven are in Te Awamutu. The tally includes 53 unlinked "mystery cases" so far.

There are 38 people in hospital today, including five in ICU or high-dependency units.

Although the numbers may have come as a shock to many New Zealanders, Professor Nick Wilson isn't surprised.

"This is not too surprising, it will probably continue until the vaccination levels in Auckland really catch up, it's sort of a race between the virus and the vaccination coverage."

Prime Minister Jacinda Ardern said cases announced today were a result of "non compliance" of alert level 3 restrictions in Auckland. Social indoor gatherings were a contributing factor to the new cases.

Ardern said she did not want people relying on vaccinations alone at this stage, and rules still need to be followed.

Although Wilson believes vaccination is the key to bringing the case numbers down, he said the Government should be looking at mandating masks inside all indoors areas, alongside looking at improving ventilation.

"We also really need to tighten the border around Auckland, so that the rest of the country has more times to increase vaccination levels, that border is far too porous," he said.

Wilson said this rise in cases may push the priority for another Super Saturday-like event, as events with free food, live music and more draw people in.

So far 158,522 eligible Aucklanders had not had a first dose of the vaccine. On Tuesday, Ardern urged people to get their second dose also if it has been three weeks since the first.

"It does look like these big events where there is free food, entertainment, live music and all sort of things does tend to help, so I think there should be serious consideration about giving it another go."

In a time where Auckland and Waikato remain at a high alert level, Immunologist Dr Dianne Sika-Paotonu said there's an unsettling growth in Covid-19 cases.

"We're continuing to see unsettling growth in Covid-19 case numbers reflecting Delta transmission within the community and across the Auckland region with the recent escalation in persistent unlinked mystery cases of unknown origin appearing," she said.

However, Sika-Paotonu's message to communities remains to be get vaccinated, get tested and follow the rules.

Māori and Pacific communities have been heavily impacted by the current Delta outbreak and as their vaccination rates remain behind the overall rate, she believes these communities must be prioritised.

"Courage in the face of adversity continues to be demonstrated by our Pacific and Māori communities and respective health workforces, who've been working tirelessly, mobilising and rallying to continue doing the work that's needed to reach some of the hard-to-reach in our communities," Sika-Paotonu said.

As accessibility continues to be an issues for hard-to-reach communities, Sika-Paotonu believes more vaccination outreach activities and events are needed.