Government and governance, Health | Australia

24 August 2021

The New South Wales COVID-19 epidemic has highlighted the divisions in National Cabinet about what vaccination level needs to be reached before Australia can relax its COVID-19 restrictions, Zoë Hyde, Quentin Grafton, and Tom Kompas write.

On 30 July, National Cabinet’s National Plan to transition Australia’s National COVID-19 Response was announced, intended to manage a shift in Australia’s pandemic response from the suppression of COVID-19 to managing the virus like other common respiratory diseases.

As part of this plan, vaccination targets for those aged over 16 were set. These targets were informed by epidemiological modelling undertaken by the Doherty Institute and an economic impact analysis by the Australian Treasury.

Currently, Australia is in Phase A of the Plan, the ‘vaccinate, prepare and pilot’ phase, with the goal to “strongly suppress the virus for the purpose of minimising community transmission”.

Once 70 per cent of the adult population is fully vaccinated with two doses of vaccine, Australia will transition into Phase B, where the goal will be to “…to minimise serious illness, hospitalisation and fatality as a result of COVID-19 with low level restrictions”.

Phase C begins when 80 per cent of the adult population is fully vaccinated, and its goal will be “…to minimise serious illness, hospitalisations, and fatalities as a result of COVID-19 with baseline restrictions”. Phase C will only allow for highly targeted lockdowns.

Finally, Phase D’s goal is to “manage COVID-19 consistent with public health management of other infectious diseases”. This final phase of the Plan is likely to be reached in 2022. At that point, international borders will reopen and there will no longer be ongoing public health restrictions or lockdowns. In other words, COVID-19 will be managed like other common respiratory diseases, akin to treating the virus “like the flu”.

Unfortunately, this National Plan to transition Australia’s COVID-19 response is back to front. Instead, the Government should establish a transition strategy based on the following three key pillars.

First, it must be built on staying below a transparent and agreed-upon maximum tolerable number of hospitalisations and fatalities, as well as long COVID cases, determined by National Cabinet.

Second, it should identify the minimum vaccination level for the total population and for vulnerable groups required to achieve public health goals. These numbers should be fully informed by comprehensive risk analyses, account for scientific uncertainty in key parameters, and be comprehensible to decision-makers.

More on this: Australia must support equitable access to vaccines

Third, it must evaluate public health and economic trade-offs – at different vaccination levels – for both the total population and vulnerable groups.

We have modelled the projected outcomes of dropping all public health measures and managing COVID-19 like the flu at different levels of vaccination.

Our modelling evaluates the effects of vaccinating children, providing a single mRNA booster (of Pfizer or Moderna vaccine) to all those who received the AstraZeneca vaccine, and vaccinating all those 60 years of age and older at a higher level than the general population – 95 per cent.

Our results are built on four key assumptions.

First, that when Australia no longer imposes adequate public health restrictions or lockdowns, everyone will eventually be exposed to the virus that causes COVID-19.

Second, we assume that Australians will face a variant that is at least as transmissible as the Delta variant, which has an estimated basic reproduction number, or R0, of six.

Third, that fatality rates will be at least as high as those observed for the original strain in 2020.

And finally, that vaccine effectiveness against infection, symptomatic disease, and hospitalisation are, respectively, for AstraZeneca: 60, 67, and 92 per cent, and for Pfizer: 79, 88, and 96 per cent.

Making these assumptions, our modelling shows that herd immunity against strains as contagious as the Delta variant can be achieved if 95 per cent or more of the entire population is vaccinated, but only if people who receive the AstraZeneca vaccine are subsequently given a mRNA booster shot.

We find that if 70 per cent of Australians over 16 years of age are fully vaccinated, but with a 95 per cent vaccination level for those aged 60 years and over, there could eventually be some 6.9 million symptomatic COVID-19 cases, 154,000 hospitalisations, and 29,000 fatalities. Notably, hospitalisations and fatalities would not be restricted to the unvaccinated.

Further, if just five per cent of symptomatic cases result in long COVID, where serious symptoms such as post-viral fatigue can persist for months or longer, and which can also occur in vaccine breakthrough infections, some 270,000 Australians could develop long COVID, even if 80 per cent of those aged 16 years and over are vaccinated.

If children are also fully vaccinated, national fatalities – for all age groups – would be reduced to 19,000, assuming 80 per cent adult vaccination coverage, and would fall to 10,000 at a 90 per cent adult vaccination coverage.

Children also benefit directly from vaccination. Our projections indicate that 12,000 hospitalisations could be prevented in children and adolescents if 75 per cent vaccination coverage is achieved in these age groups.

Giving adults a booster dose of an mRNA vaccine further improves outcomes. At 80 per cent adult vaccination coverage but allowing for an mRNA booster for all those fully vaccinated with AstraZeneca, symptomatic cases, hospitalisations, and fatalities could be much less, with our modelling predicting 6,000 fewer deaths.

Our projections of fatalities are much higher than those of the Doherty Institute used in the National Plan. The Doherty Institute, relative to our modelling, assumed: a shorter modelling time horizon, a lower assumed 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 Test, Trace, Isolate and Quarantine remains partially effective, even at very high new daily cases.

More on this: Vaccinations, borders, and the Delta variant

Our projections of hospitalisations and fatalities 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.

Our results suggest that four key vaccination steps must be followed before exposing Australians to uncontrolled SARS-CoV-2 infection.

First, children and adolescents should be vaccinated.

Second, vaccine coverage among adults aged older than 60, and in other vulnerable groups like among Aboriginal and Torres Strait Islander Australians, should be 95 per cent or higher.

Third, Australians vaccinated with AstraZeneca should be given an mRNA (Pfizer or Moderna) booster before the international border reopens or public health measures are prematurely relaxed when there is ongoing community transmission. Those vaccinated with an mRNA vaccine should also receive a booster shot, when appropriate.

And, finally, Australia needs very high vaccination coverage for the entire population, preferably more than 90 per cent, to mitigate excess deaths.

If the country achieves these four steps, fully relaxing public health measures to eliminate community transmission could still, eventually, result in some 5,000 fatalities and 40,000 cases of long COVID.

By comparison, under the National Plan, assuming 80 per cent vaccination coverage overall for those over 16 – without attaining 95 per cent coverage in those aged 60 and over – there could be 10 times as many cumulative fatalities, approximately 50,000, and some 270,000 cases of long COVID, when public health restrictions are fully relaxed.

The consequences of prematurely relaxing public health measures to suppress COVID-19, even after vaccinating 80 per cent of adults, would likely be irreversible, and unacceptable to many Australians.

National Cabinet must not squander its opportunity to devise a safe and affordable transition to a ‘post-COVID-19’ era. If National Cabinet revises its strategy to include our four vaccination steps, many lives will be saved, and many more (including children) will not suffer from debilitating long COVID.

The information contained in this article is not formal medical advice regarding COVID-19. For individual medical advice about COVID-19 and COVID-19 vaccinations, consult with your GP.

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10 Responses

  1. Nick Janes says:

    Hi,

    Interesting analysis team. You state you used a longer time horizon than Doherty, can you please advise which time horizon you used?

  2. Richard Lawrie says:

    I fail to understand the logic behind the Doherty Plan. At 70 to 80% millions will still be unvaccinated and this will be a recipe for pain suffering and death as they get the virus. OK I guess as long as you are not the one dying or suffering. If a number of states effectively control virus spread, why create a system that infects their population. We need a better plan that protects people, not one that puts them at risk. Seems money is more important than lives. My life matters, does yours.

  3. Joe Weinhardt says:

    Ladies and Gentlemen,
    I hope that you have disseminated this research widely, especially to state and commonwealth health/chief health officers, @ScottMorrisonMP and @GladysB!

  4. Daryl Daley says:

    Well done

  5. Paul says:

    Trust the outcomes not the modelling. The arguments in this article are alarmist and unrealistic. Australia will never have 95% of the population vaccinated – no country has or will. If we wait until then, we would never open up and the costs of that both personal and economic are cataclysmic. The authors lack perspective, and they have a model which doesn’t look at human behaviour, which is why all of these models systematically and massively overstate the outcomes of deaths and hospitalisations. Look at the UK and US etc which opened up with 50% of their population vaccinated, the death rates and hospitalisation rates are way below what is said in this article. So my advice – ignore these alarmists.

  6. Harry Clarke says:

    The assumption about fatality rates is unreasonable. Observed mortality post-vaccination is much lower than in 2020. This presumably drives your extreme conclusions. You should be careful about making strong claims. This is much more than an academic exercise.

  7. Margaret Colquhoun says:

    What a well-written and carefully considered article. However, with the mess the government made with the rollout of AstraZeneca and the distrust that has engendered in the minds of many seniors, the chance of vaccinating 95% of the over 60s is zero – at least while AstraZeneca is all that this group is offered.
    By the way, the spokesperson for the Doherty Institute who said that an extra 1500 deaths did not make a material difference to the modelling did their Institute and its argument no favours.

  8. Aaron K Neufeld says:

    Such a good article, uts clear and logical. However, why is there no discussion about the variability in the model and it’s limitations more explicitly. A model is never going be right, otherwise we wouldn’t need a model. The model should produce outcomes that help an understanding of what variables create the greatest degree of uncertainty and the magnitude of that uncertainty. This article does not reveal enough of what the model can predict in that sense.

  9. David Potter says:

    You can use real world data from the UK to verify your modelling. Currently 77% of over 16s are fully vaccinated. Cases currently rising, and 147 deaths yesterday. Obviously there are differences between UK and Australia:
    [a] Higher proportion of AZ vaccinations relative to Pfizer.
    [b] Much more ‘natural immunity’ from previous infection than we have in Australia.
    [c] Minimal restrictions.
    [d] A 30 billion pound test and trace regime.
    etc etc.
    But it makes it clear that your modelling is, unfortunately, in the correct ball park.

  10. Peter Jones says:

    How to you reach 90% vaccination among a population in which 17% say they will NEVER take a vaccine?

    The maths don’t add up. You cannot let 17% hold the rest of the country hostage, the point being opening up should happen once everyone has been offered the vaccine. If people decline then that’s their choice.

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