• New Zealand has become the latest country to abandon a "zero Covid" strategy, a decision that comes as the delta variant of the virus proved too potent to stop.
• A "zero Covid" policy is one that seeks to eliminate community transmission of the virus.
• Experts say the highly infectious delta variant makes that tricky.

LONDON — New Zealand has become the latest country to abandon a zero Covid strategy, with the virus proving much harder to stop now the highly infectious delta variant is dominant.

After adopting one of the world's strictest approaches to trying to control the spread of Covid-19, New Zealand announced on Monday that the country would no longer pursue an approach that would attempt to eliminate all Covid cases.

This zero Covid strategy, also employed by the likes of China and Taiwan, involves strict lockdowns (even after the detection of just one or a handful of cases) and extensive testing, heavily controlled or closed borders, as well as robust contact tracing systems and quarantine mandates.

The move comes after a lockdown in the city of Auckland failed to stop the virus in the face of the more virulent delta variant. It is estimated to be 60% more transmissible than the alpha variant originally discovered in late 2020, and which itself usurped a previous, less infectious version of the virus.

New Zealand has been notoriously strict in its tackling of Covid; Prime Minister Jacinda Ardern put the entire country under a strict lockdown in August after a single suspected case of Covid caused by the delta variant — at that time the country's first coronavirus case in six months — was reported in Auckland.

But on Monday, Ardern said that the city's lockdown would be eased gradually and that the country's strategy towards tackling Covid was changing.

"For this outbreak, it's clear that long periods of heavy restrictions has not got us to zero cases," Ardern said during a press conference.  "But that is OK. Elimination was important because we didn't have vaccines. Now we do, so we can begin to change the way we do things."

Ardern said it was important that the country maintain strict controls, however, saying it still needed to "contain and control the virus as much as possible, while we make our transition from a place where we only use heavy restrictions to a place where we use vaccines in everyday public health measures."

Why it's not working

It's the first time that New Zealand has publicly signaled a shift away from a zero Covid strategy, coming after its neighbor Australia also abandoned its zero tolerance, or "Covid zero" approach in early September, saying it had shifted to a position of "learning to live with" the virus.

Similarly to in New Zealand, Australia's decision to abandon the strategy came after a strict lockdown in Melbourne railed to quell an outbreak there. 

At the time, Victoria state's Premier Daniel Andrews noted that "we have thrown everything at this, but it is now clear to us that we are not going to drive these numbers down, they are instead going to increase."

Experts are not surprised by the shift in strategy, noting that the spread of the delta variant makes such approaches futile.

"It's no surprise that New Zealand has abandoned its 'zero covid' strategy – the highly transmissible delta variant has changed the game and means that an elimination strategy is no longer viable," Lawrence Young, a virologist and professor of molecular oncology at the University of Warwick, told CNBC Monday.

"That doesn't mean that NZ's and Australia's robust approach to managing the pandemic – strict border restrictions, quarantine measures and strong contact tracing – hasn't been effective but continued heavy restrictions are damaging to individuals and society," he said.

Zero tolerance policies will become harder as the rest of the world opens up, he added, but stressed that doesn't mean people shouldn't remain vigilant. "We need to stop the virus spreading and mutating by doing everything we can to support the global roll out of vaccines."

Trying to completely suppress the spread of Covid-19 has often been questioned by experts, but in countries where vaccination rollouts have been slower, lockdowns have served to slow, if not eradicate, the spread of the virus.

Defending the Auckland lockdown Monday, Ardern said pursuing a zero Covid strategy had been the "right choice and the only choice" for Auckland while vaccination rates had remained low, with only 25% of Aucklanders fully vaccinated at the time.

Now, seven weeks later, she said that 52% of Aucklanders were fully vaccinated, with 84% having had one dose. Clinical data shows that full vaccination against Covid-19 is highly effective at protecting people against severe Covid infection, hospitalization and death.

Zero Covid adherents

Zero Covid strategies remain in place in China, Taiwan and Hong Kong, however, with none of them showing signs of relinquishing it just yet. Other Asian economies that have adopted similar approaches include Macau, Singapore, South Korea and Vietnam.

The data shows that this strategy has helped keep cases and deaths in the region much lower than in Europe and the U.S. The latter has seen the highest death toll from Covid in the world, with over 703,000 deaths.

On Monday, Taiwan's Central Epidemic Command Center said there had been zero new local cases of Covid-19 and five imported ones, marking the fourth consecutive day without a local infection.

On the same day, Hong Kong also recorded four new cases (all imported, continuing a trend seen in recent weeks), while China reported 26 new cases of confirmed infections on Monday, again, with all of them cited as imported cases, although the accuracy of China's data during the pandemic has been questioned.

Experts in the region say there's good reason for not giving up on zero Covid strategies yet, particularly when vaccination rates are patchy.

David Hui, a professor at the Chinese University of Hong Kong who leads an expert committee that advises the government, told CNBC that Hong Kong won't reconsider its zero-tolerance Covid-19 strategy to one of "living with the virus" until the vaccination rate is higher.

"In contrast to Singapore, [the] U.K. and other Western countries, the overall vaccination rate in Hong Kong is too low (67% with one dose and 62.9% of population fully vaccinated with two doses) to adopt living with the virus. The vaccination rate among those aged 70 years or over is around 30%," he said.

"If we live with the virus, many elderly unvaccinated subjects will develop severe disease and our healthcare system will collapse."

The Economist Intelligence Unit noted in a report in July that it expects zero‑Covid markets in Asia to retain tight border controls throughout 2021, only loosening from early 2022 when mass vaccination is achieved.

"Deaths among 'zero Covid' countries in Asia have been much lower than global peers and the economic impact less severe, contributing to a much shallower recession in Asia in 2020 than in other regions," it said, noting that, "if the rest of the world had adopted a similar approach, zero‑Covid might prove a sustainable strategy. However, it now risks becoming one that will undercut rather than support economic activity as the global economy reopens."

Still, the EIU noted, the policies ultimately adopted by zero‑Covid countries will still be more conservative than those in force in North America and Europe. "The approach is likely to target "low Covid", with the approaches currently taken by Japan and South Korea serving as potential models," it said.

The EUI believed China and Taiwan were the economies in the strongest position to maintain a zero‑Covid strategy, owing to their low reliance on cross border flows of capital and talent.

Correction: This article has been updated to correct Hong Kong's vaccination rate in people aged 70 and over.