New Zealand's restrictions during the pandemic saved the lives of about 20,000 people, according to new research.

The paper by 16 leading doctors and scientists, published in the New Zealand Medical Journal on Friday, is calling for all serious respiratory infections - including influenza and RSV - to be treated the same way.

Lead author and Otago University public health professor Michael Baker says it was a "strange paradox" of preventative medicine that its success could work against it in people's minds.

"We have an expression in public health: 'A public health triumph: nothing happened'.

"If you stop a pandemic, or greatly blunt it, people may say 'well, what was all the fuss about?'"

More than 3000 New Zealanders have died from Covid-19, and it is on track to kill 1000 people this year, making it the country's most deadly infectious disease at the moment.

However, compared with other nations, New Zealand has got off extremely lightly.

Globally, there have been about 29 million deaths in the past three years, says Baker.

"I've recently been overseas for the first time in three years, and colleagues in Europe were talking about how miserable and horrible that time was, when they were seeing even healthy, middle-aged colleagues dying of this infection, that is frontline health workers.

"We were spared that.

"If we'd had the mortality rate of the United States, for instance, we would have had 20,000 people die over that period."

As the report noted, the key to New Zealand's success was keeping the virus out for two years until most people could be vaccinated and the health system was ready for it, he says.

Report co-author and Canterbury University statistician professor Michael Plank says with the advantage of hindsight, some things could have been done better.

But decision-makers had to act quickly, based on the information they had at the time.

"In terms of the big decisions, like closing the border, going into that strict lockdown right at the start in March 2020, I think the evidence shows they were the right decisions to make," says Plank.

The big lesson from the pandemic was the need to be better prepared, he says.

Frontline medical staff, lab scientists and others had been "in emergency mode" for the past three years, he says.

"They've been working under such pressure, it's led to high levels of fatigue and burnout.

"So we really do need to invest in research, science and public health so that we are better prepared for the next public health emergency or pandemic when it does arrive."

Immunisation Advisory Centre medical director professor Nikki Turner says high vaccination rates helped keep the death toll low.

"New Zealand overall has done really well, but I think people now have got quite short memories and are forgetting how effective it was," says Turner.

"And we still have the impact ongoing effect of Covid and other respiratory viruses."

Vaccination rates typically surged whenever people understood the risk - but often that did not happen until an outbreak had actually started.

"The problem is we're trying to sell the absence of disease, which is a difficult product to sell," says Turner.

"But we still have a lot of Covid, a lot of respiratory disease, and if our community is aware and engaged in the conversations and can see for themselves the damage on the community, then vaccines have a really important place."

The experts agreed just because Covid was here to stay, that did not mean New Zealanders needed to accept infections as inevitable.

The report advocates a strategic approach to all respiratory infections, including vaccinating at-risk people, improving air quality and wearing masks in some settings.

Baker says the Royal Commission of Inquiry into the Covid-19 response - which was due to deliver its report to the government next September - would lay out what needed to be done to manage any future pandemics.

"I think we would do some things the same, but every New Zealander would want us to learn lessons and do it better next time," he says.

"Unfortunately, there are even worse threats on the horizon.

"If we had a pandemic like the 1918 influenza for instance, that would be 1 percent of the population dead in two months, that's 50,000 people."

- Ruth Hill/RNZ.