Covid-19

Virus could have killed 80,000 without NZ lockdown

Analysis: New modelling from the University of Auckland indicates Covid-19 could have killed 80,000 New Zealanders if we took no action to stop it, Marc Daalder reports

New projections from the University of Auckland offer a stark image of the damage Covid-19 could do to New Zealand and show why the lockdown is so important: it could save tens of thousands of lives.

The numbers, produced by researchers at Te Pūnaha Matatini, the University's data-focused Centre of Research Excellence, indicate if no action was taken to fight the spread of the disease, there would be 10 times as many patients requiring hospital treatment as there would be beds and staff to treat them. Nearly 90 percent of the population would become infected and 1.67 percent of New Zealanders - 80,000 - would die.

Based on overseas findings

The modelling reflects the findings of a groundbreaking paper published by academics at the Imperial College London which concluded that taking no action to fight the virus could leave 250,000 dead in the United Kingdom and 2.2 million in the United States. Taking "mitigation" measures - known cases self-isolate, as do their families and all people over 70 self-quarantine - would only halve the death toll. But "suppression" measures, which would involve reducing physical contact to the bare minimum, working from home and closing schools, can cut the toll by 90 percent.

As this Newsroom analysis shows, these suppression measures would have to be in place more or less constantly until a vaccine is ready - approximately 18 months away. They could be relaxed slightly when cases dropped for a short period of time - roughly two months on lockdown, one month off - but this would have to be carefully monitored to avoid an outbreak that would overwhelm the health system and spiral out of control.

These estimates, when presented to UK and American officials, helped change government policy there. In New Zealand, as Newsroom reported, the same figures have been very influential in resetting the Government's strategy towards Covid-19.

Mitigation won't work

The University of Auckland paper comes to similarly stark conclusions. Mitigation strategies - for example, just closing schools and universities or ensuring the isolation of cases and their families - would only cut the mortality rate by a fraction of a percent. Even the most optimal mitigation would still lead to cases requiring hospital treatment exceeding capacity by a factor of six. Nearly 60,000 New Zealanders would die.

Through implementing long-term suppression strategies - namely, population-wide social distancing through a measure like a lockdown and closing schools and universities - the mortality rate could be reduced to 0.0004 percent, or just 20 deaths.

Those measures would have to be in place long-term, however, or else the mortality rate would shoot back up.

This chart from the University of Auckland paper shows strict controls could keep case numbers low, but infections would spike after controls were lifted.

The paper also examined the possibility of relying on a "herd immunity" strategy, which would involve allowing enough Kiwis to contract the virus to render the population at large immune. This could be done in a staged manner, snapping suppression controls into place to prevent hospital capacity from being overwhelmed and then relaxing them when the number of cases decreased.

However, the researchers concluded this would require reducing the rate of spread of the virus to below one - in other words, each person who has it would have to infect less than one other person. "There is no evidence that it has yet been achieved in comparable, western democracies, including those that have instigated major lockdowns such as Italy," the authors write.

Advantages of suppression

"A major advantage of suppression strategies as opposed to mitigation is that early suppression buys time. This has two key benefits: (1) it may be possible to delay the epidemic for long enough that a vaccine and/or effective treatment become widely available in NZ; and (2) it allows NZ to learn from rapidly unfolding events in other countries."

Suppression could also be managed to allow for the eventual lifting of some restrictions.

"If strong suppression is successful in reducing the number of cases close to zero, it is possible that some control measures could be lifted. This would require: (i) continued widespread testing and contact tracing to ensure there are no undetected case clusters; and (ii) strong border measures to remain in place to ensure no fresh infections are imported," the researchers write.

"As long as (i) and (ii) are in place and we are confident that there are no undetected cases, this could allow periods when schools, businesses and services can operate and many aspects of day-to-day life to continue."

This is the strategy the Government is currently pursuing, as this Newsroom analysis explains. If the lockdown can reduce cases to zero and the borders remain closed - or secure enough to admit no new Covid-19 cases - then restrictions can be eased as long as we are constantly vigilant for any new infections.

Either way, however, we will have to live our lives differently, conscious of the risk the virus poses, for a while yet to come.

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