Covid 19 coronavirus: Earlier lockdown in Victoria could have eliminated virus, researchers say

Victorian Premier Daniel Andrews responded to the state's second wave of Covid-19 by introducing restrictions in specified suburbs rather than establishing a complete lockdown. Photo / AP

A decision back in July could have helped Victoria eliminate Covid-19 and likely move out of lockdown faster, according to new modelling.

Analysis of modelling of Victoria's coronavirus crisis suggests elimination could have been achieved across the state if the government had immediately implemented stage 4 lockdown from July 9.

The research, which was led by professor of epidemiology at the University of Melbourne Tony Blakely, was published in the Medical Journal of Australia (MJA) on Monday.

Analysis of the modelling found elimination was possible for Victoria, adding that if it was achieved it "would have been optimal for health and for the economy in the long term".

The first cases linked to Victoria's second wave were detected in late May/early June, and the true extent of the new outbreak became apparent in the weeks following.

As a result of the wave of new infections, metropolitan Melbourne and the Mitchell Shire were sent into what was meant to be a six-week stage 3 lockdown on July 9.

The research suggests Victoria could have eliminated the virus if it went straight into stage 4 lockdown for six weeks on July 9. Photo / News Corp Australia

However, cases continued to rise, prompting the tougher stage 4 lockdown to be introduced for Melbourne on August 2 and regional Victoria placed in stage 3 lockdown from August 6.

Stage 4 lockdown meant most things apart from essential businesses were shut, a night-time curfew was imposed, a 5km travel radius introduced, and strict rules around being in public were put in place.

Masks were also made mandatory for everyone in Victoria, apart from those with a medical exemption.

The research paper examined three modelling scenarios and analysed how Victoria would have fared under each approach.

The first was a standard approach which was equivalent to keeping stage 3 lockdown but without masks, then there was a standard approach with mask use at 50 per cent, followed by a stringent approach with masks at 50 per cent, and finally a stringent approach with mask use at 90 per cent.

The final approach was the most similar to the stage 4 lockdown introduced in Melbourne, except without the curfew or 5km travel restrictions.

The modelling published in the paper showed the fourth policy approach had the highest percentage of reaching elimination by August 19. Image / Supplied

The analysis found that under the "standard" policy approach, which is what was first implemented in Melbourne on July 9, there was "no chance" all infected people would be cleared of the virus by the time the six-week stage 3 lockdown ended.

The modelling also predicted there was a zero per cent chance of achieving elimination by the lockdown deadline with the "standard with masks at 50 per cent" approach.

The probability for elimination was slightly higher for the "stringent with masks at 50 per cent" approach, with 4 per cent chance of elimination.

The approach most similar to stage 4 lockdown was the most promising, with the "stringent with masks at 90 per cent" showing a 30 per cent possibility of elimination after six weeks.

Looking at the probabilities of the last actual virus infection occurring by August 19 when the six-week lockdown would end, meant the figures became significantly more promising.

This change put the probabilities at 0 per cent, 1 per cent, 45 per cent and 90 per cent respectively.

The probabilities became even more promising if the aim was to reach the last date of community transmission by August 19. Photo / Supplied

Researchers conclude that had the decision been made to go into a form of stage 4 lockdown, even without the curfew and travel restrictions, it was possible Victoria could have achieved elimination.

"Undertaking simulation modelling of Sars-CoV-2 policy options is challenging and the uncertainties are still considerable even when using the best estimates available," the paper stated.

"Nevertheless, our results lend weight to the proposition that elimination was achievable if Victoria had gone into stage 4 lockdown with mandatory wearing of masks immediately from July 9."