COVID-19: Jacinda Ardern says she's considered localised lockdowns for Auckland, but implementation difficult

Despite just three sub-clusters of coronavirus in the community, the entire Auckland region remains in alert level 3.

And with just eight new community cases of the virus reported on Tuesday, Prime Minister Jacinda Ardern is being asked if she's considering switching to localised lockdowns.

These could be implemented on a suburb-by-suburb basis, controlling movement where clusters arise while allowing the rest of the city and region to move back towards economic and social freedom.

But speaking at her press conference on Tuesday, Ardern said there were problems with making sure localised lockdowns "provide the level of safeguard that you would want in order for them to be effective".

"We have discussed that and considered that. There's a lot of complexity in some of the clusters we have a the moment and their reach hasn't always been totally localised and so that's been one of the complications," Ardern explained.

"We've been open to considering that option all the way through but with the clusters we've had to date, they have often reached beyond single suburbs and so you would run the risk of trying to take a localised approach that could essentially lead to an outbreak getting worse elsewhere."

Ardern passed the baton to Director-General of Health Dr Ashley Bloomfield, who said he agreed with Ardern's summary.

"In a city like Auckland where people do move around even between adjacent suburbs to access essential services it can be very tricky to do it in a localised way," he said.

Suburb-by-suburb lockdowns were tried in Melbourne last year at the end of June but failed to stop a second wave that killed hundreds of people. 

"Melbourne attempted to contain an outbreak last year with suburb-specific lockdowns and it didn’t work," University of Canterbury disease modeller Michael Plank told Newshub in March.

"Unfortunately the virus doesn't know about postcodes and people often live, work and socialise in different parts of the city, bringing the potential for the virus to spread. In Melbourne, this meant the lockdowns were always a step behind the virus and the end result was a much longer lockdown being needed for the whole city."

And University of Auckland disease modeller Shaun Hendy also told Newshub when a cluster is discovered, "the chances that the cluster extends across the city is relatively high".

"Aucklanders tend to work, study, etc a long way from where they live, so distant suburbs are often very connected. Because of this, an early post-code lockdown is risky unless you are confident you know something about the chain of transmission."

He said it's possible postcode-specific restrictions could possibly work when lifting levels, however.

"That being said, it is very difficult to enforce lockdowns at the post-code level. You'd be relying mostly on public compliance and it would probably lead to a lot of confusion."