Prime Minister Jacinda Ardern has revealed Cabinet's decisions about when and how Covid-19 restrictions will be eased.

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Ardern is joined by Associate Health Minister Ayesha Verrall.

Ardern says the traffic light system will remain help manage any future outbreaks.

However, she says things have changed since the system was introduced: we're now dealing with Omicron, rather than Delta; we have more data now and are better able to identify which environments are high risk; and we have high rates of vaccination coverage.

With that in mind, Ardern says she is announcing that all outdoor gathering limits will removed from the traffic light system.

She says indoor gathering limits will increase from 100 to 200 under the red light setting.

Ardern says data shows hospitality had a relatively low secondary attack rate of 6.7 percent, which is backed up by other research.

She says it's the view of public health officials hospitality gathering limits can be increased in the red setting from 100 to 200 without having a significant impact on the health system, particularly when retaining the seated and separated rules.

She is also announcing that vaccine passes will no longer be required from 11.59pm on 4 April.

Businesses and events will still be able to use them, if they choose to do so, but they will no longer be mandated, she says.

Ardern says masks are vital, and while people do not like them - for good reason - a study from the British Medical Journal late last year showed mask wearing reduced new cases by 53 percent.

In Orange, outdoor events will also be limitless. Close contact is higher risk for indoor events however so organisers of events over 500 people are encouraged to either add extra capacity or provide seating.

Green will not have restrictions but there will be guidance, and will not change.

"These changes are based on the best available evidence we have right now in real time. We believe they will make the Covid Protection Framework easier to maintain while also still being very effective," Ardern says.

She says the changes can be made almost immediately and will come into effect at 11.59pm on Friday.

On mandates and vaccine passes, Ardern says she was initially not in favour of their use but after months of Delta it became clear that mandates were needed to achieve vaccination levels required for safe reopening, and passes had a role to play too.

She says these were undoubtedly one of the reasons we reached 95 percent of the eligible population vaccinated, and achieved the near elimination of Delta over summer, but Omicron has changed things.

Almost all of New Zealand's more than 500,000 cases of Covid-19 have been in the Omicron wave, she says. Many cases do not show symptoms and testing does not catch every case, so modellers expect total cases now could be as high as 1.7 million.

For the unvaccinated, the illness can be severe, she says.

Ardern says these people will have built some immunity from the illness itself, and as we come down off the peak the need for passes changes.

Looking back

Ardern says after two long years of living in a pandemic it's easy to lose sight of how far New Zealand has come.

"This exact day two years ago, Director General of Health Ashley Bloomfield announced from over at the Ministry of Health that we had 36 new cases of Covid-19. Half at that time were from overseas travel, with the exception of the Queenstown World Hereford Cattle conference ... we could contact trace 50 new cases a day back then. We hadn't locked down yet, but the early signs were there."

She says two new community cases were announced on 23 March 2020, one in Wairarapa with no link to the border.

Within days New Zealand was in a nationwide lockdown, a decision Ardern says was not a hard one.

"We had no other defence, no other way to protect each other. There was no vaccine, no antiviral medicines, there was very little data to tell us which public health restrictions worked and which did not, so we built our own defences and we hunkered down."

The transition has not been easy but it has worked, she says. New Zealand successfully eliminated the first wave and recorded the lowest number of deaths in the OECD for two years in a row.

She says the response was also the best economic response, but while we've been successful "it was also bloody hard ... everyone has had to give up something to make this work and some more than others".

She says she imagines every family will have had a difficult conversation about vaccines, mandates or passes but among the different opinions there is also fatigue.

Ardern says we are now able to keep moving forward safely, but we have to keep in mind that Covid is here to stay.

Ardern says for most people now symptoms are minor and they've recovered well at home, but others less able to fight the virus it meant a threat to their lives. Experts believe the case numbers have peaked in Auckland now, and the rest of the country is expected to follow in the next couple of weeks.

She says after the peak we will fall back to a steady rolling baseline of potentially several thousand cases a day, and there are likely to be spikes particularly over winter.

"We need to continue to use tools that can keep our vulnerable community safe, such as those who are immunocompromised and those with disabilities ... there are ways we can do that while continuing to move forward."

Cabinet has been seeking advice on the vaccine mandates, passes, the traffic light system, and all Covid-19 restrictions now that New Zealand appears to be nearing or passing the peak of Omicron cases, and made decisions in their Monday meeting.

More to come...