WHO adviser left ‘heartbroken’ by Doherty Institute COVID modelling

The Doherty Institute’s modelling, released on 3 August and fully agreed to by National Cabinet on Friday, has been used to underpin the Federal Government’s first vaccination targets as part of a four-phase plan to move from Australia’s suppression strategy to reopening. But it has received mixed responses.
 
Professor Ivo Mueller, Co-Division Head of the Population Health and Immunity Division at The Walter and Eliza Hall Institute, welcomed the modelling, saying it ‘strikes a delicate balance’ between managing health risks, economic costs and personal freedom.
 
But others are not so sure.
 
Led by Doherty Institute Director of Epidemiology Professor Jodie McVernon, the modelling sets a goal of vaccinating 70% of Australians aged 16 and over to move to Phase B, which will allow Australia to manage the virus with low-level restrictions and lockdowns ‘unlikely’.
 
To get to Phase C, the target increases to 80%, at which stage it is expected minimum ongoing baseline restrictions will be employed with lockdowns rare, allowing for freer movement of people, including no restrictions on out-bound travel for vaccinated Australians.
 
With these numbers, the modelling estimates that over the first 180 days after community transmission is established that there could be up to 1984 deaths at 70% coverage and 1281 deaths once 80% is reached.
 
But Professor Mary-Louise McLaws, a UNSW Medicine infection control expert and adviser to the World Health Organization (WHO) Infection Prevention and Control Guidance Development Group for COVID-19, says she was left heartbroken when the modelling was announced.
 
‘Over a thousand deaths is acceptable? We’re reeling now from the 22 deaths [in the current NSW outbreak]. We are aiming at a low bar,’ she told newsGP.
 
‘They have modelled the likelihood of controlling an outbreak in Australia at a level of 70% uptake of the vaccine – and that 70% is 70% of 80% of the population. That’s effectively one in two people fully protected.
 
‘It assumes that one in two people vaccinated, plus public health interventions that are non-pharmaceutical, will protect the other one in two that aren’t vaccinated, and at the moment, we’re seeing that this just isn’t the case.’
 
With those aged 19 and under accounting for 15% of confirmed COVID cases in Australia, now that Pfizer has received TGA and ATAGI approval for at-risk children as young as 12, Professor McLaws believes Australia should follow the UK and US’s lead by vaccinating this cohort.
 
The modelling concluded that expanding the vaccine program to the 12–15 year age group ‘has minimal impact on transmission and clinical outcomes for any achieved level of vaccine uptake’.
 
However, it did suggest a strategic shift to bringing forward vaccination for those aged 16–39.
 
‘As supply allows, extending vaccinations for adults under 40 years offers the greatest potential to reduce transmission now that a high proportion of vulnerable Australians are vaccinated,’ the modelling states.
 
It was in April that Professor McLaws suggested a similar strategy to newsGP. But with the emergence of Delta, she says her stance has changed.
 
‘With Delta, without having at least one dose of a vaccine, the viral load is on average about a thousand times higher than an infected person has ever developed before with any previous strain,’ Professor McLaws said.
 
‘Therefore, it’s highly infectious indoors, in a school, in a school room, and in a playground where kids don’t keep physically distant.
 
‘Does Australia really want to challenge this virus and think that anyone under the age of 16 will be protected with one in three people, in general, unprotected? Why wouldn’t you start rolling it out to the 12-year-old’s, who we have approval for in Australia?’
 
Professor Emma McBryde from the Australian Institute of Tropical Health and Medicine at James Cook University agrees.
 
Recent modelling undertaken by the infectious diseases physician, which has yet to be peer-reviewed, found that targeting 18–30-year-old’s after the elderly is the best strategy. It also found that teenagers impact on herd immunity.
 
‘My group starts with an assumption that the effective reproduction number, before vaccination, could be as high as five, and if it is, then we need to vaccinate children to achieve herd immunity,’ Professor McBryde said.
 
‘The Doherty Institute assumes that the reproduction number … is only 3.6. If we model this, we get the same findings, but the results are highly sensitive to the assumed effective reproduction number.’
 
And while a recent study suggests children rarely get long COVID, Professor McLaws says this should still be taken into account alongside the potential benefits in terms of reaching herd immunity.
 
‘We don’t really know what happens. We don’t know if they bounce back very easily,’ she said.
 
‘So why would we want to do that to a future generation of leaders? Why give them, potentially, a chronic illness, particularly during this exciting time of their youth? We really do have, don’t we, a duty of care to the young?’
 
With the pandemic constantly evolving, the Doherty Institute’s modelling does acknowledge that the possible emergence of ‘vaccine escape’ variants may require a ‘re-evaluation of targets and associated requirements for public health measures’.
 
But Professor McLaws thinks following the model could lead to exactly that.
 
New data that breaks down vaccine coverage by Statistical Areas Level 4, released by the Department of Health on Tuesday, has revealed inequity.
 
If this continues and children are left out, with lockdowns ruled out and reliance placed on contact tracing, Professor McLaws fears it could create a breeding ground for the emergence of a new variant. 
 
‘This [model] has failed to take into account a variant of concern, the speed at which it moves, the fact that … children are now an important vector,’ she said.
 
‘If you’re going to apply this “one in two” rule, you better be sure that there’s one in two people in every single local government area [that is vaccinated] and that there’s no inequity.
 
‘And, you better be absolutely certain that that doesn’t hit a sweet spot for mutation. Do we really want to develop an Australian variant?’
 
Instead, Professor McLaws is adamant that Australia should be more aspirational.
 
‘I’ve been at WHO meetings where we are focusing on variants of concern for infection prevention and control, and the whole world’s worried about it and taking it very, very seriously,’ she said.
 
‘So I am just so surprised that our leaders are prepared to forego an aspirational level. I can only assume that something’s holding them back, and that something has to be availability or a fear of hitting a roadblock for uptake. But why put a roadblock there with a low bar? Why not go for gold?
 
‘I hope I’m wrong, and I hope that the European modellers that looked at this sweet spot are wrong as well. But let’s not test this.’
 
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