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Tue, 8 Sep 2020

Lockdowns essential to prevent third wave: JCU researcher

Stick notes on a window saying
Dr David Kault's calculations show an extended lockdown is needed to end community transmission. Photo: Anastasiia Chepinska, Unsplash

New analysis shows an extended lockdown in Victoria is necessary to avoid a third wave of COVID-19 infections, and NSW should consider lockdowns and compulsory masks.

GP, mathematician and James Cook University adjunct senior lecturer Dr David Kault has calculated how lifting restrictions at different stages would affect infection rates in Victoria, and the results show an extended lockdown is needed to end community transmission.

“If all restrictions were lifted while there is still community transmission from unknown sources, there is a high chance of a third wave in that state,” he said. “Even if those cases dropped to an average of only one per day, there’d still be less than a 2% chance of avoiding a third wave.

“However, if restrictions were to be maintained for another three weeks since the last date of community transmission, there is over 96% chance that that no further cases of community transmission will emerge.”

Dr Kault said his calculations assume that contact tracing is not an effective alternative to lockdown in preventing the virus spread, and tracing teams becoming overwhelmed when case numbers increase.

“Contact tracing is only moderately effective compared to a lockdown,” he said. “This is why the contact tracing approach in NSW, that’s dealing with far fewer cases than Victoria, has only managed a marginal reduction in community transmission in a month, compared to Victoria where lockdown has reduced infection ten-fold over this time.”

Dr Kault said luck plays a big part in the effectiveness of contact tracing.

“If a person is a superspreader and spreads the disease to a few other superspreaders then contact tracing can easily become overwhelmed,” he said.

“My calculations suggest that Victoria should extend its lockdown by a further week and that NSW should implement compulsory mask wearing and lockdown for a few weeks if further cases of community transmission from an unknown source are detected.”

Dr Kault argues that elimination remains possible in Australia and that people shouldn’t ignore the mortality rate.

“Six states and territories of Australia, New Zealand, and a number of nations in East Asia and the Pacific show that elimination is absolutely achievable,” he said. “The experience in the rest of the world suggests that a huge COVID-19 mortality rate is a more likely outcome of not aiming for elimination.”

Dr Kault said the claim that economic lockdown would lead to a worse mortality rate than the virus due to suicide was untrue.

“In New Zealand it is reported that there was actually a drop in the usual rate of mortality during their lockdown,” he said.

“The argument for opening now, rather than making the small additional effort to achieve elimination, does not make any sense in terms of health and only makes economic sense if one’s horizon is less than the four weeks it will take for the third wave to emerge.”


Dr David Kault