The arguments for reducing the COVID-19 booster shot down to three months

Take a bow New Zealand for pulling up your sleeves - 4 million Kiwis have now had two jabs and we've hit 90 percent vaccinated in every age group over 12.

But our booster campaign needs a booster, with modelling showing we could hit 80,000 daily cases a week before 80 percent of adults are eligible for their third shots. 

The stats show boosters are dragging - 1.83 million people are now eligible for their third shot but 672,865 - 37 percent - still haven't got it. 

"To anyone, four or months or more, who had their second dose, please go out and get your booster today," Prime Minister Jacinda Ardern said on Thursday.  

But more people would be eligible if the gap was reduced to three months.

"We really want to be rolling out the booster to as many people here as possible as soon as we can," says Otago University Professor Michael Baker, an epidemiologist. 

New modelling predicts an Omicron outbreak peaks six weeks after it first gets into the community, meaning we could hit 80,000 daily cases by the first weekend of March.

But with the four-month booster window, we won't have 80 percent of adults eligible until March 12 - after the onslaught.

If that window was three months, 80 percent would be eligible on February 12 and fully immunised two weeks later - right at the peak.

"The decision on the gap for boosters is one for medical experts - not one for politicians. If they advise us to do that then that's what we'll do," Ardern said. 

National leader Christopher Luxon doesn't understand what the hold-up is. 

"The brief should be given to the public health experts - go scan the global best practice research that exists all around the world and tell us within a 24 hour period whether it's three months or four months," he told Newshub. 

It's worse for Māori - their vaccination rates were slower so most can only get their boosters in March.

"That's simply too late, we'll likely be inundated with Omicron cases well before then," says Māori COVID-19 data analyst Dr Rawiri Taonui.

But Omicron and booster protection aren't an exact science. 

Immunologist Nikki Turner told Newshub getting the booster at four months gives the best protection, so shortening it to three might not actually be as good a defence against the impending outbreak.