As COVID-19 rampaged through the elderly in the darkest days of 2020, vaccinating children seemed a distant prospect.
But a new dynamic, driven by the highly infectious Delta strain, is already shaping up to define the latter stages of 2021.
With more than a quarter of Victoria's active cases now in children aged under 10, a 15-year old dying while infected with the virus in Sydney, and outbreaks centred in schools in the ACT, it is increasingly apparent young people are in the new variant's sights.
Delta is shifting the goalposts, but experts are split on prioritising vaccinations for children.
But Australia's path out of lockdown still hinges on an 80 per cent full vaccination rate for those aged 16 or above, roughly 65 per cent of the total population.
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UNSW infectious disease expert Mary-Louise McLaws warns Delta has already made that target obsolete.
"All models need to keep up with changes in pandemics," she tells The Canberra Times.
"The Doherty model needs to be updated, because there's clear evidence that children are more at risk from the Delta variant than from any other previous strain.
"It hasn't factored in the real importance of young adults, adolescents, and now children. So it needs to be redone."
Although vaccination began with older Australians, McLaws warns against the "dangerous" belief that the vaccination rate alone accounted for Delta's spread among children.
Anyone who says clearly that children should be vaccinated is unaware of how complex that decision is.Infectious disease expert Nigel Curtis
"This variant has adapted ... and can get around their wonderfully fresh, young immune system," she says.
"Anyone who's in the contagious stage produces, on average, 1000 times more viral load than with previous strains."
McLaws has recommended young people take AstraZeneca to avoid severe illness, but says Australia will need to shift to mRNA jabs, which are more effective at preventing transmission.
"You need as much Pfizer or Moderna as possible into the arms of 16 years to 39 years of age, but preferably 20 to 39. Then you go to the 16 to 19s, and then you go to the 12-year-olds," she says.
But Nigel Curtis, an infectious disease expert at the University of Melbourne and Murdoch Children's Research Institute, says it remains unclear whether Covid is shifting its focus.
"I'm not sure that we can say Delta is targeting children any more than it's targeting adults. It's targeting everyone, so we're seeing more disease in all age groups. But we're still seeing that very marked gradient in severity [in older people]," he says.
While the danger of the vaccine is clearly dwarfed by that from Covid for adults, Curtis says the risk-balance equation for healthy children, less likely to suffer severe illness, was much less clear.
"Anyone who says clearly that children should be vaccinated, or clearly they shouldn't, is just unaware of how complex that decision is," he says.
"The benefits [of vaccinating them] may be more for the long-term consequences ... but we don't know yet how big a problem they are in children.
"There's still a lot of unknown. We simply don't have enough data yet to accurately balance the risks and benefits in that younger age group."
And with some adults - the most likely transmitters - still unable to access a vaccine, he says child immunisation is a "moot point".
"The one silver lining of being slow to vaccinate in Australia is that we can benefit from the experience of the countries that are ahead of us," he says.
The Grattan Institute's Stephen Duckett, who led the Health Department under Paul Keating, wants vaccinations for under-16s as quickly as possible, but agrees supply may be an issue.
"It seems to me the public would want children to be prioritised in a rollout. The virus doesn't somehow stop and check whether you're 15 years old before it infects you," he says.
Duckett says rapid antigen tests, which can produce a result with 15 minutes, should be used to create a layered protection at schools.
Although they are less accurate than their "gold standard" PCR equivalents, he stresses they can be administered and read without a pathologist.
"It is an order of magnitude cheaper to do a rapid antigen test than a PCR test, which means you can do 10 times as many for the same cost," he says.
"The fact you can do it every day, or every second day, at school is worth a lot."
The TGA has approved over 20 forms of antigen testing but, unlike in the UK and US, they have not been given the green light for self-use.
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Duckett warns a more cohesive system for online learning is needed in the interim, with school closures disproportionately impacting disadvantaged children.
"Parents are probably going to be risk averse about their kids going to school in an environment where they could get infected. There's an immediate consequence of that," he says.
The Prime Minister insists the best way for parents to avoid infections in their children is to get vaccinated themselves.
ANU infectious diseases epidemiologist Meru Sheel agrees adults remain the most likely source of infection in children, even with outbreaks occurring in school settings.
"[But] Delta has changed that a little bit, and we are seeing child-to-child transmission a little bit more. To what degree, I'm not sure," she says.
Sheel says the factors driving outbreaks in young people are not uniform across jurisdictions. Young people in NSW are more likely to be essential workers and, by extension, travel more widely during a lockdown.
"In the ACT it's a little bit different ... These outbreaks have occurred in closed school settings. It's Canberra winter, so there's a lot of time spent indoors and that's likely influencing some of this," she says.
It's going to take a shift from the community to participate in the new normal, because Covid is here to stay.Epidemiologist Meru Sheel
But she believes Delta's spread among children has moved the goalposts on vaccinating the young, which initially did not seem a pressing need.
"I definitely think it will have to happen sooner than five years time, which we may have thought six months ago," she says.
But Israel is showing even world-leading vaccination rates only stem the spread of Delta. Around 80 per cent of the 12-and-over population is fully vaccinated, but the country is suffering one of the world's highest infection rates.
And Sheel warns pockets of Covid will emerge sporadically, requiring similar responses seen when measles or influenza outbreaks occur. She warns habits developed during the pandemic will linger well after population-wide vaccination is achieved.
"We'll probably still have to accept a new normal, and go up and down with mass gathering cancellations, mask use, respiratory and hand hygiene," she says.
"It's going to take a shift from the community to participate in the new normal, because Covid is here to stay, most likely."
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