Booster shots appear to be the difference between mild and deadly fourth waves of the COVID-19 pandemic, says Jacinda Ardern, urging Kiwis to get theirs before winter arrives.
The current wave of infection is centred on Europe, with global daily case numbers currently at a similar level to the third wave's peak, but still rising.
Thankfully the daily death toll has remained flat at about 7000, the fourth wave proving to be less fatal so far than those which came before. In fact, each successive wave of the pandemic has seen lower mortality, as more of the world gets vaccinated.
But with evidence - both in the lab, and in the real world - that the vaccines' efficacy drops off over time, many countries have started rolling out booster shots.
"When you see those countries that are experiencing those fourth waves, you can see that in many cases they haven't started a booster campaign or they're only just starting," the Prime Minister told The Hui on Monday.
"It does seem to be the thing that's making a difference."
The World Health Organization has urged an end to booster rollouts, saying doses would be better off going into the arms of the unvaccinated in places like Africa to stop more variants like Omicron from emerging.
But nations that can afford to, such as New Zealand, are ploughing ahead - and the evidence suggests Ardern's assessment is correct.
Chile leads the world in the booster rollout, with nearly half of its entire population having a third dose of the Chinese-developed SinoVac already. Its booster campaign began in early August, before Delta even arrived in New Zealand. Its latest outbreak peaked at just over 2500 cases a day, far short of previous waves, with little increase in mortality.
Uruguay's booster rollout isn't far behind, and it hasn't had a new wave of infection at all - consistently posting daily figures not far off New Zealand's for several months now.
Israel, which had a fast initial vaccine rollout that stalled at just 64 percent of the population, used a combination of mask mandates, vaccine passports and a supercharged booster campaign to get its biggest outbreak to date under control - dropping from 11,000 cases a day in September to a few hundred a day now.
Much of Europe lags behind, with booster coverage of just 17 percent in Germany and 13 percent in France and Norway, forcing leaders to consider new restrictions and tougher vaccine mandates.
New Zealand's booster campaign began just over a week ago, and already more than 100,000 have had theirs. Ardern said the timing works out well for us.
"The advantage New Zealand has is that we can watch them a season ahead. They're coming into their winter and doing it tough. We've got the opportunity now in the safety of summer to make sure we are reaching all of our older citizens and making sure they're having their booster. It's really, really critical. It brings your immunity back up to where it was when you were first vaccinated."
While anyone can get the booster once they're eligible, that's likely to be most elderly people at first, since they had first dibs on the vaccines in early 2021.
While it's still early days, the evidence to date suggests the new Omicron variant is better at infecting vaccinated people than previous strains - but the vaccine still offers strong protection against serious illness and death, making it more important than ever to get.
Ardern told host Mihingarangi Forbes she wouldn't be satisfied "so long as there's someone who is eligible and hasn't been [vaccinated]".
"So there's been a huge focus on making sure that we are reaching everyone wherever they are in the country, and ensuring that we are overcoming those barriers. We're now up to 83 percent first doses for Māori, and chasing those second doses. But in my mind so long as there's people who are eligible who haven't been vaccinated, we've got work to do."
