Ending lockdowns with 80% vaccinated could cause 25,000 Australian deaths, new modelling suggests

Australia’s national plan to end lockdowns once 80% of the adult population is vaccinated could result in 25,000 deaths in total and 270,000 cases of long Covid, new modelling warns.

The work by researchers at three leading Australian universities predicts more than 10 times as many deaths as the Doherty Institute modelling that underpins the national four-phase roadmap. That plan was adopted by national cabinet in July but is subject to different interpretations by state and territory leaders.

The Doherty modelling looked at the number of deaths in the first 180 days of reopening at the 70% and 80% thresholds that lead to phase B and C – when lockdowns would be “less likely” and then “highly targeted”.

The latest research models total cumulative deaths over a longer time frame during phase D of the national plan – when no restrictions remain.

Dr Zoë Hyde, an epidemiologist and co-author from the University of Western Australia, warned the new modelling – which is yet to be peer-reviewed – showed it was “simply too dangerous to treat Covid-19 like the flu” and that Australia should reach higher vaccination rates before opening up.

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Hyde and co-authors Prof Quentin Grafton of the Australian National University and Prof Tom Kompas of the University of Melbourne, both economists, called for a 90% vaccination rate among all Australians, including children, and a 95% rate for vulnerable populations, including elderly people and Indigenous Australians.

On Monday, Scott Morrison continued to urge state and territory leaders not to deviate from the 70% and 80% targets to reduce, and then phase out lockdowns. The prime minister argued that by then vaccination rates would be higher among elderly people.

But there are still significant reservations about ending lockdowns and border restrictions among predominantly Labor-lead states including the high rates of transmission in children, the high case numbers in greater Sydney spreading interstate, and low vaccination rates among Indigenous Australians.

The federal government is preparing a school-based vaccination rollout for children aged 12 to 15, but Morrison has ruled out counting them in the national plan targets.

The Doherty modelling suggests that in the first 180 days after Australia reopens at an 80% of adults vaccination rate, there would be 761 deaths with partial testing, tracking, tracing and quarantine.

In their paper, published on Tuesday, Hyde, Grafton, Kompas and independent modeller John Parslow found that reopening at a 70% vaccination rate could result in 6.9 million symptomatic Covid-19 cases, 154,000 hospitalisations, and 29,000 total deaths.

It warned that if Australia reopens once 80% of adults are vaccinated, which translates to 65% of the population overall, there could be approximately 25,000 fatalities and 270,000 cases of long Covid.

If Australia reopens with 80% of adults vaccinated and all children vaccinated, estimated deaths would fall to 19,000, or to 10,000 if 90% of adults were vaccinated.

The Doherty modelling produced less dire results due to different assumptions: a shorter time horizon; a lower proportion of symptomatic infections; lower transmission among children; baseline public health measures that reduce the reproduction number from 6.32 to 3.6, and that testing, tracing, isolating and quarantine remains “partially effective”, even at very high new daily cases.

Grafton defended those differences, explaining the group had assumed hospitalisation and deaths would continue “until everyone is infected”.

“That would be in 2022, some time in phase D when there are minimal public health measures and no lockdowns. [Covid-19] will go everywhere, it’s extremely contagious,” he told Guardian Australia.

Grafton warned the greatest danger would be to regional and remote areas with low vaccination rates and high Indigenous populations, such as western New South Wales, Arnhem Land, and the Kimberley.

“We have a serious problem. In Sydney, there are still enough ventilators and you can get to the hospital in 30 minutes. In these communities: forget it. Many people there have underlying co-morbidities. Unless we do something different it is a nightmare coming our way.”

Grafton said the group’s modelling recognised that Delta was “highly transmissible with children”, arguing it was a “real problem” to exclude 5 million people by setting vaccination targets based only on the population aged 16 and over.

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The Doherty Institute disagreed, concluding that including children aged 12 to 15 “would not materially change the expected overall health outcomes” because the “total number of Australians who experience severe illness … will be similar”.

Grafton said that tracking, tracing, isolating and quarantine was “no longer effective” once daily cases exceeded 100 a day and that NSW daily case numbers of more than 800 showed it was “clearly not working in any meaningful way at the moment”.

The Australian Capital Territory territory chief minister, Andrew Barr, has warned that even in phases B and C when 70% and 80% vaccination rates had been achieved, public health measures would remain, such as density limits.

Grafton said density limits, social distancing and masks would help but would not reduce the reproduction rate by half.

The researchers have suggested vaccinating children and adolescents, giving mRNA booster shots to all Australians including those who had taken AstraZeneca, and reaching a vaccination rate of 90% overall and 95% among vulnerable populations.

Those measures could reduce deaths from Covid to 5,000 and cases of long Covid to 40,000, their modelling suggests.

Kompas said the projections “would have been even worse if we had used the higher preliminary estimates of the increased virulence of the Delta variant”.

“This means our projections likely represent a lower estimate of the cumulative public health outcomes of fully relaxing public health measures at phase D of the national plan, or sooner, if outbreaks are not effectively suppressed or eliminated,” he said.

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On Monday, Morrison said the Doherty’s Institute’s Prof Jodie McVernon had advised the government that the starting point of the number of community cases “does not influence the overall conclusions of the model” about reopening at the 70% and 80% benchmarks.

Morrison told reporters in Canberra that unvaccinated Australians would be “protected to a degree by the fact that the broader population is more generally vaccinated”.

Australia’s deputy chief medical officer, Prof Michael Kidd, said there was a higher proportion of positive children under 16 in the current Covid outbreaks “due to the increased transmissibility of the Delta variant, the rapid spread … among household members” and higher rates of vaccination among adults.

“We are still seeing much higher rates of hospitalisation among older people with Covid-19,” he said in a statement. “The data continues to show that, thankfully, our children are at much lower risk than other Australians.”