In March 2020, Europe was declared the "epicentre" of the COVID-19 pandemic by the World Health Organization (WHO) before fighting back to keep the virus at bay.
Now, 18 months later, the continent has again been given that disaster-evoking label, with cases shooting to peak levels in some countries despite relatively high rates of vaccination.
It's such a drastic u-turn for the continent that it's triggered a sudden rethink by governments about their COVID-19 responses.
From ensuring boosters are quickly rolled out, to keeping up basic health measures like mask-wearing indoors, experts Newhsub spoke to say Europe's ordeal may provide some valuable lessons to New Zealand as we begin easing our restrictions.
Denmark's COVID resurgence
The resurgence in Denmark is of particular note as just two months ago, life there seemed to be getting back to pre-COVID-like normality.
After pulling back on requirements like mask-wearing on public transport and lifting limits on gatherings, its government brazenly proclaimed the virus was no longer a "critical threat" and did away with vaccine passes.
That announcement came in mid-September, when about 83.5 percent of Danes over the age of 12 were fully vaccinated - one of the highest rates in Europe.
There were jovial scenes across the nation as it got its own version of freedom day and COVID went from being an intrusion to an afterthought for many. The Scandinavian country hosted Europe's first concert since the pandemic began with a crowd of more than 50,000 people; photos of the attendees packed into the mosh pit a symbol of Danes' renewed liberties.
Unfortunately, though, it appears it was to be just a brief reprieve.
Infections in Denmark have risen dramatically since restrictions were dropped. The seven-day rolling average has jumped from 520 on September 10 to nearly 4000. And just like that, the country's 'corona passes' are coming back.
This week, the country's health minister said the government was seeking to re-introduce masking on public transport and in stores and would also accelerate a booster vaccine programme.
The dramatic change in fortunes for Denmark comes despite it having a relatively high level of vaccination compared to others in Europe, at least when looking at percentage of the eligible population. Even after the requirement to use vaccination passports was removed, the country's rate increased to 86.3 percent of those over 12 being fully vaccinated.
That's not to say, however, that vaccinations aren't having an impact on softening COVID's blow. While daily case numbers are now surpassing last December's highs, deaths remain far below their peak in January. The seven-day rolling average at the start of this week was six deaths compared to 32 earlier this year.
Europe closing back down
The risk for the unvaccinated is clear, as demonstrated by data in New Zealand showing that of 15 people to die with COVID-19 this outbreak, just three were fully vaccinated. Most hospitalised people also didn't have two doses.
Dr Nick Wilson, a specialist in public health at the University of Otago, told Newshub that was also seen in Europe.
"I think if you look at those countries, the people who are ending up in hospital are virtually entirely the unvaccinated. The situation would be extremely more severe if they hadn't achieved those high vaccination levels.
"Although the case numbers are soaring, there are fewer hospitalisations than during the earlier pandemic waves and fewer people ending up in ICU and dying. But people are still ending up dying in ICU largely because they haven't been vaccinated."
But the concerning growth in cases in Denmark isn't an isolated issue. Instead, it's a serious scenario being observed across western Europe at the moment, including in other countries which thought their days of tight restrictions were over.
Portugal, where nurses were previously talking about running out of people to vaccinate, is bringing back measures in the face of rising infections. The Netherlands, where nearly 85 percent of adults are fully vaccinated, is back in a form of lockdown with restaurants closed past a certain time. Ireland, which began lifting some restrictions in October, has asked locals to return to working at home. Other countries, particularly in eastern Europe, with relatively low vaccination rates, are struggling to an even greater extent.
Speaking about the uptick in cases this month, Dr Hans Henri P. Kluge, WHO's Regional Director for Europe, said vaccines are a "powerful asset" but must be "used alongside other tools" like contact tracing and physical distancing.
He noted that if 95 percent universal mask use was achieved in Europe and central Asia, "we could save up to 188,000 lives of the 500,000 lives we may lose before February 2022".
Countries in the region should "carefully reconsider easing or lifting" measures at the moment, Dr Kluge said.
What does this mean for New Zealand?
Throughout Aotearoa's COVID-19 response, we've had the advantage of being able to study the experiences of other countries before facing issues ourselves.
The situation unfolding in Europe provides another opportunity for New Zealand to understand how COVID-19 can return, even when most people have had two jabs.
Prime Minister Jacinda Ardern is clearly keeping an eye on it, telling Parliament this week Europe, "a region that has access to vaccinations in the same way we do" has been warned by WHO about its perilous position.
"In parts of Europe, there are vaccination levels we would consider high that are moving into lockdown. We need to continue to listen to the best research and advice possible, and that is what we are doing."
We're unable to draw an exact comparison between the situation in, say Denmark, and New Zealand. For one, Denmark, a Nordic country, is entering winter when the virus naturally is more likely to spread due to people being indoors, while New Zealand is heading into summer.
But there are lessons to be learned.
One of those should be around what we consider a 'high vaccination rate', Dr Helen Petousis-Harris, a vaccinologist with the University of Auckland, says. She believes it's critical to focus on the actual number of people unvaccinated and identify rates across the total population.
Just considering the percentage who are fully vaccinated amongst the eligible may provide a false sense of security when the number unvaccinated remains large, she says.
"I think you have to move away from that percentage and think about, numerically, how many people have you actually got, because that's where you're seeing it," Dr Petousis-Harris says. "You're really seeing this problem mainly among the unvaccinated and there just happens to be numerically a lot of them."
For example, while 86.3 percent of Denmark's eligible population is fully vaccinated, it drops to 76 percent when taking into account the total population. That leaves more than a million Danes unvaccinated overall, including those who aren't yet able to get the jab.
Dr Petousis-Harris says New Zealand can't just forget about vaccinating when we get to 90 percent.
"Even when you get to 90 percent, like in New Zealand, there are still hundreds of thousands of people and Delta will find everybody," she says.
COVID-19 modeller Professor Michael Plank agrees, saying while vaccination rates in some European countries are getting up there, "they're a long way from 100 percent".
"Young children can't be vaccinated, so that sort of creates a portion of the population that can have quite high infection rates and they spill over into other age groups," he told Newshub.
Prof Plank also puts the rise in cases in Europe down to "the evidence of waning immunity".
"A lot of these countries started their vaccine rollout so early in the year, so [it's been] several months since the bulk of those populations were vaccinated.
"What the evidence shows is that immunity against becoming infected with the virus does decline over time and so gradually that just makes it easier for the virus to spread."
While some European countries, like France and Germany, have been offering boosters, the uptake has been low. But in the face of case growth, the European Centre for Disease Prevention and Control this week told governments there needs to be more urgency with administering the top-up shots to people over 18. It was previously only focused on getting boosters to the vulnerable.
That waning immunity and slow rollout hopefully won't be such an issue in New Zealand, with boosters available here from November 29. Anyone over 18 who had their second dose more than six months earlier will be eligible.
"The booster programme is going to be crucial and we're going to need a really big push on this to get everyone who's had their first two doses back for that booster shot as soon as they are eligible, which is six months after that second dose," Prof Plank says.
"The data on boosters is really, really good, and it shows that you actually get to a level of immunity higher than after just the first two doses, and it looks like it may last a bit longer as well. So the boosters are really effective. We just need a really strong push on getting those booster doses out to people."
Dr Petousis-Harris said protection from the first two shots against severe disease doesn't appear to be waning significantly, but it is when looking at "the ability to become infected".
"If you give a booster, you'll improve people's resistance to getting infected before transmitting it. So that helps everybody. It will also improve their own protection against even mild disease."
While events in Europe show getting children vaccinated and rolling out booster shots is a priority, Dr Wilson said it shouldn't happen without governments also taking other steps.
"The situation in Europe should really focus our minds not only to get very high vaccination rates in New Zealand and to have boosters and to protect the children as well with vaccination, but we've really got to maintain a range of interventions."
That was also the key message from WHO chief Tedros Adhanom Ghebreyesus this week. He said the first round of vaccines have provided a "false sense of security", leading some countries to believe that they no longer need to consider other precautions.
"No country is out of the woods," he said.
Dr Wilson said it's clear from the experience of the Danes that simply dropping all restrictions is not a wise move. Instead, we need to keep up measures such as physical distancing, masks in indoor environments and making structural improvements to things like ventilation.
"The New Zealand government has actually been taking a fairly cautious approach. I would have preferred if they had really tried harder to eliminate COVID outside Auckland and have a stronger boundary around Auckland. But still, a pretty good job is being done with controlling spread outside of Auckland.
"We're not making the same mistakes as the UK did, basically throwing out every intervention. Denmark was, I would have thought, a bit reckless in how they just gave up on everything, especially those things which prevent seasonal influenza and other infections like masks and improve ventilation."
On Friday next week, all of New Zealand will move to the COVID-19 Protection Framework, better known as the traffic light system. For different parts of the country, this will mean different things, but for all, vaccination certificates are central and there will be no free-for-all abandonment of measures.
Dr Wilson says we should also look at other countries in our own hemisphere for lessons. He noted that in Australia, New South Wales was opening up without seeing any surge in cases which may reflect its "mass vaccination efforts". NSW also still has mask rules in place, requiring them in stores and on public transport.
Prof Plank agreed New Zealand's "cautious approach is warranted".
"The framework we're moving into gives us a system where we can manage some of those risks. Obviously, we're going to have vaccine passports. I think that's going to be one of the key tools in the toolkit that would allow us to reopen and allow businesses and schools and so on to be open, but to have some to retain some control over the spread of the virus."
New Zealand also benefited from our easing of restrictions coinciding with summer.
"This is probably a relatively low-risk time of year when we can start to ease some of those restrictions. As we go into next year and we start to approach winter, we need to be prepared that the virus could start to spread again as we move into those colder months."
While some European countries hit a vaccination target then tried to move on, Prof Plank says vaccines can't be relied on by themselves.
"The vaccine is really good and without the vaccine, we'd be in a much, much worse condition, but we still need other measures alongside the vaccine.
"Hopefully we can mainly use less disruptive measures, things like masks, contact tracing, testing, ventilation, those sorts of things to mitigate the risk without having to use lockdowns.
"Lockdowns are the thing that everyone is desperately trying to avoid. The way to do that is to have as high a vaccination rate as possible and to make really good use of some of those other tools."
Dr Petousis-Harris agrees public health measures need to go hand in hand with vaccines.
"Absolutely. What we saw overseas is a lot of places just threw absolutely everything out and said, 'Right, let's go'. Of course, we saw what we would expect to see.
"It has to be a gradual thing. We need to maintain and use the tools we've been given to to ease our way there. So not all at once. Throwing it all out at once, it will just go 'woosh' - and it will find all of those hundreds of thousands of people in particular."
"So we've got the vaccines, we've got potentially the boosters, we've got these really good looking new drugs that if used early, they can help prevent severe disease.
"I know the basics are boring, but all those things together are what makes a difference - not just relying on vaccinating 65 percent of the population."