The numbers game: what triggers COVID-19 lockdowns and freedoms?

For the second time in a week, yesterday NSW recorded more new daily COVID-19 cases than Victoria.

In Sydney, masks have all but been abandoned, with restrictions on outdoor venues and concerts about to be eased. In Melbourne, residents are still confined to their houses for 22 hours a day. 

Greater Melbourne has been subject to one of the longest and harshest lockdowns in the world, despite case numbers dropping to single digits. This morning, the state recorded seven new cases in the past day.

There’s still a way to go before Melbourne reaches a rolling 14-day average of five new cases, which was the trigger point Premier Daniel Andrews had set for the lockdown to be eased.

This benchmark will now be reviewed, after harsh criticism of Andrews, who conceded the current case numbers may be “as good as it gets”.

What should Victoria’s benchmark be, and is Andrews’ approach more politics than science?

What’s worked elsewhere?

Risk assessment

New Zealand focused on risk assessments in its roadmap to recovery. There are four stages ranging from single or isolated cluster outbreaks to sustained and intensive transmission.

The country was slow to ease restrictions, waiting until no new cases were reported for 17 days, but fast to implement them, locking Auckland back down following nine cases of community transmission.

The country’s response has been lauded as one of the most successful in the world.

No definitions

In comparison, Australia’s federal approach seems to avoid assessments of any kind — a three-step framework has restriction guidelines but leaves it up to states to assess how well they’re doing.

NSW followed this approach, with no risk assessment criteria or case number thresholds. Restrictions were eased on May 14 following a week of one or fewer daily cases with an unknown source.

There was a lot of uncertainty about the future when NSW cases started to creep up again in July, hitting a high of 22 with one unknown and 17 locally-acquired cases. Kirby Institute immunovirology Associate Professor Stuart Turville told Crikey his team was on high alert.

“We saw that as a warning, we didn’t know how it could track. We all said we were on a tipping point — there was an element of concern,” he said. 

Numbers thankfully soon tracked back down.

The UK has followed suit in avoiding fixed rules. After recording 13,972 new COVID-19 cases on Monday, with cases spreading across the country, a tiered lockdown system will be implemented. 

The UK’s approach, La Trobe University epidemiology Associate Professor Hassan Vally told Crikey, was too little too late. 

“The UK has waited too long. A delay of even a few days can mean the difference between saving many lives,” he said.

Play by the numbers

Both Victoria and Spain have opted for a numbers-based approach to lockdown rules.

In Spain, restrictions are imposed in areas with more than 100,000 residents based on three benchmarks: if there were 500 cases per 100,000 inhabitants, 35% COVID-19 patient occupancy in intensive care units, and positive results in 10% of tests.

Victoria has similarly opted for a numbers-based approach, despite not initially having clear rules about when a lockdown should be implemented. 

When cases started increasing again, Victoria scrambled to try different tactics, first locking down specific postcodes, then shires, before shutting down the entire state.  

Now, the roadmap is clear. Greater Melbourne must reach a rolling 14-day average of fewer than five cases before restrictions will be eased. 

Was five ever feasible?

Many have been critical of the five-case goal, flagging early on such a strict benchmark may not be feasible.

Critics have stressed the approach is one of elimination rather than suppression, with 500 doctors signing an open letter stressing the ongoing lockdown was causing more harm than good.

“It was raised at the time that Victoria’s five-day threshold was a really tough criterion to meet and it’s playing out like a lot of people predicted,” Vally said.

“It was going be tough to get there and the plan needed more flexibility.” 

Flexibility is key 

Vally stressed that in all cases, flexibility was key, with infection sources more important than the numbers itself. 

“The word narrative which the government keeps using is important. We need that understanding of what cases we’re seeing, how many are linked to other outbreaks, and the level of threat,” he said. 

Importantly, he added, Australia has fared well compared to the rest of the world thanks so swift — and strict — action.

But whether “as good as it gets” will be Victoria’s claim to freedom remains to be seen.