The arrival of vaccine passes appears to have prompted more Kiwis to get their jabs – putting New Zealand on course to reach a double-dose rate of 91 per cent by New Year.
Experts have also put the bump down to concerns over nationwide community transmission, possible fears over the emergence of new variant Omicron, and health workers' hard work that's noticeably lifted coverage among Māori.
After weeks of declining vaccination counts, the Herald's vaccination tracker predicted there'd be around 49,000 second doses last week.
Instead, some 95,000 were administered – a near two-fold bump of 46,000.
That momentum was now expected to continue, bringing total coverage among the currently eligible to 89 per cent by next week, 90 per cent by December 20, and 91.3 per cent by January 1.
As at today, some 3.7 million eligible Kiwis (87.9 per cent) were now fully vaccinated, while 3.9m people (93.4 per cent) had received at least one dose.
That left some 277,773 people – or 6.6 per cent of the eligible population – completely unvaccinated.
Immunisation Advisory Centre director Dr Nikki Turner said the simplest explanation for the rapid bounce would be the introduction of vaccine passes, which came into force on December 3 when New Zealand moved to the new traffic light system.
"It will also be down to people becoming more aware of the traffic light system and what it means for their own personal lives."
Turner said more people might also be concerned about the likelihood of the virus spreading into the regions.
"We're all now getting into the Christmas holidays – and there's a growing awareness around the country that we're not safe," she said.
"Added to that is the new international concern around Omicron, and the fact that we know it's going to spread into the New Zealand community."
Finally, Turner pointed to a groundswell of work by vaccinators in Māori and Pacific communities, whose respective coverage rates had climbed from 57 per cent and 72 per cent a month ago to 72 per cent and 85 per cent today.
"New Zealand's really put a lot of resources and effort into much more creative approaches at the community level - particularly with Māori and Pacific communities - in a way that we've never done so extensively before."
Importantly, vaccination rates among young Māori and Pacific had been building over the past few weeks.
"We know that younger people are probably the hardest group in the world to vaccinate – especially when we have ethnic gaps – and it's a huge credit to New Zealand that it's learned by responding to community health providers, and trialled new things."
Otago University epidemiologist Professor Michael Baker agreed that vaccine passes appeared to have compelled more people to get vaccinated.
"Some people may have had a fear of vaccination, even if they're not actually anti-vax, while others might not have been very organised, and thought they could put it off as long as possible," Baker said.
"So, the new mandates may have turned people to thinking, I want to be fully vaccinated by the time I head off to visit family and friends around the country."
In other cases, people simply may have faced access problems, such as having limited mobility, or busy lives.
Baker expected New Zealand would soon hit the point where the bulk of people still to be vaccinated were those against it.
Encouragingly – and despite vast amounts of misinformation circulating on social media platforms like Facebook and Telegram - that demographic has been narrowing over time.
As at October, the Ministry of Health's most recent survey period, the overall potential uptake - including those already vaccinated and those likely to get vaccinated – was 92 per cent, up five per cent from September.
Of the remaining respondents, two per cent were unsure about getting the vaccine, two per cent said they'd be unlikely to, and four per cent said they definitely wouldn't get it.
Turner emphasised the difference the vaccine made in preventing transmission, hospitalisation and death.
"The absolutely incontrovertible international evidence is, the more vaccinated you are, the less hospitalisation and less death you have – and that's exactly what New Zealand is showing. So, go us."
Interestingly, there was little sign that the new vaccine pass and traffic light regime was also encouraging more people to scan QR codes on the NZ Covid Tracer app.
Instead, University of Auckland data expert Dr Andrew Chen said, a sizeable increase in scan counts had been observed the week before the passes came into effect.
"The reasons for this are not immediately clear to me yet, but it would seem that folks were moving around a bit more in the lead-up to the Covid-19 Protection Framework, rather than there being a lot of pent up demand and pressure suddenly being released last Friday," Chen said.
"I would need to see some more data to back this up, but my suspicion at this point is that mobility didn't actually increase that much."
Chen said there remained a "usability challenge" in getting people to present their vaccination pass for verification by the venue, and then scanning the QR code themselves for their own records.
"If someone is only going to do one of these two, it's going to be the vaccination pass," he said.
"We'll need another week or two to see if the vaccination passes has a positive, negative, or neutral impact on scanning of Covid Tracer QR codes."