Should vaccine experts be needled over rollout failures?17th July 2021
“Now, when the case numbers increase, as you’ve seen from ATAGI now, their advice changes. People have understood that, but I think it has created some confusion in the public.”
To be clear, ATAGI modelled three scenarios based on a low, moderate and high level of COVID exposure, where “low” is similar to the infection rate of the national first wave, “moderate” is similar to Victoria’s second wave and “high” is similar to Europe’s January 2021 conditions.
The danger of COVID is then compared to the real but extremely rare danger of thrombosis-with-thrombocytopenia syndrome (TTS) associated with the AstraZeneca vaccine, which is more common in young people. This modelling is publicly available.
Australia had very low infection rates in April when ATAGI changed its advice to make Pfizer the preferred vaccine for under-50s, and in mid-June, when that changed again to under-60s. Now the situation has changed, at least in Sydney.
Consequently, ATAGI updated its advice last week to stress that in an outbreak area where access to Pfizer is constrained, people under 60 “should reassess the benefits to them and their contacts” from getting vaccinated with AstraZeneca.
ATAGI also reduced the recommended interval between AZ doses for people in an outbreak area; from 12 weeks to between four and eight weeks. People who had their first dose more than four weeks ago should arrange their second dose “as soon as possible”.
The debate is whether ATAGI’s initial approach should have given more weight to the likelihood of this kind of outbreak occurring, and therefore prioritised wider, faster vaccination – even at the risk of more cases of TTS. There is also significant consternation about the vaccine hesitancy caused by the constant revision of medical advice.
Associate Professor Chris Berg, an economist at RMIT University, argued ATAGI’s risk model was “woefully inadequate”. “They seem to be just taking a snapshot of exactly where we are right now and the likelihood of getting COVID exactly right now and the danger of the vaccine exactly right now,” he said.
That might have made sense when thinking about the risk of the flu, which is relatively static, he said, but not in the context of the rapidly evolving coronavirus pandemic.
“You can model an economy in equilibrium or you can model an economy that is changing,” Berg said. “It seems like they’ve just taken this static equilibrium without calculating the actual risk, which is: will there be an outbreak in 12 weeks or not?”
Changing the advice once there’s an outbreak is “nonsensical”, he said, because the outbreak has already happened and there will be a long lag before anyone caught up in it gets the protection of both jabs.
Professor Michael Sherris, of the University of NSW School of Risk and Actuarial Studies, notes that in general risk modelling “you do need to be forward-looking and you can’t just assume that because something hasn’t happened it’s not going to happen”.
Professor Terry Nolan, who heads the Doherty Institute’s Vaccine and Immunisation Research Group, chaired ATAGI from 2005 to 2014. He acknowledges the shifting AstraZeneca advice has affected people’s confidence in the vaccine – including among over-60s, for whom AZ is still the preferred jab.
“I don’t think that’s ATAGI’s fault though,” Nolan says. “You don’t [avoid] a recommendation because you’re frightened it’s going to harm confidence. This sort of recommendation was very similar to the ones made elsewhere.”
Nolan says ATAGI is doing its best and the root cause of our woes, “boring as it is”, is that we don’t have enough Pfizer vaccines. “They may have made mistakes in terms of judgment [but] from my point of view I don’t think they’ve done anything seriously wrong,” he says.
In Nolan’s view, which he has expressed before, when it became clear Australia’s Pfizer supplies would be crunched, ATAGI and the government should have changed tack to deliver as many first doses to people as fast as possible, instead of holding back second doses.
“The English and the Canadians made a decision early on [to] get as many people under one dose as they could quickly. That in retrospect was a very good decision … we should just learn from them,” Nolan says.
“As a country we possibly got it wrong early this year in taking it too easily, believing we’d be OK, we’d be safe. Increasing the pace with which we tackle all of this … would have helped us.”
ATAGI chair Allen Cheng – an infectious diseases physician, professor of epidemiology and until recently Victoria’s deputy chief health officer – makes several points in response. Firstly, ATAGI’s advice applies nationwide and has to best fit the national situation at the time. The risk calculus in Geraldton, for example, hasn’t really changed compared to the calculus in western Sydney.
You don’t [avoid] a recommendation because you’re frightened it’s going to harm confidence
Professor Terry Nolan
There were a lot of unknowns in April and it was “difficult to frame” the advice accordingly. Cheng also says the calculus is slightly more nuanced than just risk of TTS versus risk of COVID.
“The question is: between now and when you would otherwise get access to Pfizer, what is that risk [of an outbreak]? One of the unknowns is ‘when is that point in time?’ We think it’s probably the last couple of months of the year, but we don’t know for sure.”
ATAGI’s advice on AZ puts a premium on individual circumstances and individual risk assessment. To critics, this undermines the broader community goal of getting out of the pandemic quickly. But Cheng says it is important to let people decide themselves, with assistance from their GP, given the “material risk” of TTS.
”If the risk was really very small then I don’t think we’d have any hesitation in recommending for the benefit of the community that everyone get vaccinated fast,” he says. [Last week he tweeted: “If an SCG full of younger people got vaccinated, there might be 1-2 cases of TTS.“]
Cheng says ATAGI considered the change advocated by his predecessor, Terry Nolan, to delay second Pfizer doses to the six-week maximum and get more first jabs into arms. “We did think about that,” he says. “[But] in the context of a Delta outbreak you want that second dose protection.”
English studies have indicated the second Pfizer dose massively increases protection against symptomatic infection by the Delta variant. The same data showed the second AZ dose also significantly increased protection.
As for Morrison’s comments about ATAGI’s changes delaying the rollout, Cheng says there have been a number of factors in the relatively slow uptake of vaccines in Australia. He concedes the many changes to the medical advice have reduced public confidence in the AstraZeneca vaccine.
“We knew that at the time,” Cheng says. “But we’re trying to provide the best advice we can to make sure that we’re doing this as safely as we can.”
Australian Bureau of Statistics research released on Wednesday found 15 per cent of unvaccinated Australians named “wanting a different vaccine to what is available to them” as one of the factors impacting their ability to get the jab. That figure rose to 35 per cent for people aged 50 to 69, and 26 per cent for those aged over 70.
One of the nation’s foremost vaccine communication experts, University of Sydney professor Julie Leask, says ATAGI acted impeccably and took all of the relevant factors into consideration in its decision-making.
“They weighed the very real, known effects on hesitancy in the population that would come, as well as the impact on Pacific Island country neighbours where there was more COVID and this could also trigger hesitancy,” Leask says.
“In a sense they took a middle ground. They didn’t say AZ was banned. They kept the option open. They were careful to say this is based on a particular context and that context could change.”
As Leask points out, ATAGI gives the technical advice, politicians announce it – as Morrison and his Health Minister Greg Hunt did at a hasty and dramatic 7.15pm press conference in April. And the media was quick to amplify rare clot cases and interview scared people.
“The message about AZ not being banned for under-50s was never clearly communicated from there on,” says Leask. “That meant that when the PM said ‘by the way when you’re under 40 you can have the vaccine’ – that was always the case. The question was whether the GP or hub would offer it if you were under 40.”
Leask also cautions that the effect of the advice changes on hesitancy should not be overestimated.
“It’s not as big an impact as everybody assumes. We’re often going on the stories and anecdotes of people who are spooked by these announcements, and they’re highly available to the media.”
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