Covid-19: Delta strain changes AstraZeneca risk calculations for young people

The 'Oxford Vaccine' has been the main pathway out of lockdown in the Covid-ravaged UK, but has received the worst kind of publicity here over the remote risk of serious, sometimes fatal, blood clotting in young people.

But the calculation is quickly changing, and now factors in contracting the hyper-contagious Delta strain.

The death of Adriana Midori Takara, a 38-year old with no pre-existing conditions, in Sydney this weekend put a human face to reality: a virus which does not only target the elderly.

That fact has prompted 169,000 under 40s (including this reporter) to receive at least one AstraZeneca dose.

The chance of a sudden outbreak in Canberra, given its porous border to NSW, and the long-term impacts of Covid have began to outweigh the odds of a blood clot for some.

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In Sydney, that calculation has become even more stark; The city's outbreak has killed 10, outnumbering deaths linked to AstraZeneca across the country.

Again, the Australian Technical Advisory Group on Immunisation has shifted its advice.

The new message in NSW: get any vaccine you can, as quickly as you can.

Stephen Duckett, who led the Health Department under Paul Keating, said that advice should remain limited to NSW, where it reflected the worsening "environmental risk of catching Covid".

"The balance of risk is such that AstraZeneca is an acceptable vaccine [in NSW], especially given we do not have adequate supplies of Pfizer in the country yet," he said.

"In other states, I would still be saying that [under 60s] should wait for Pfizer."

While the risk of the contraceptive pill was "objectively" higher than from AstraZeneca, the way people understood the threat was more complex.

"They perceive risks that they control, or that they are familiar with, as less important than risks they don't control," he said.

"Trying to shift those perceptions is very, very hard."

Infectious diseases expert at the ANU Peter Collignon said the chance of dying from AstraZeneca, a "very effective" protection, was roughly one-in-a-million overall.

"You've got a lot of other things you do every day that are higher risk than that," he said.

The decision was "easy" for 80-year olds, who faced a one-in-ten chance of dying if they contracted Covid-19.

But for people aged in their 30s, whose odds improved to one-in-10,000, the situation became "a bit more complicated".

"If you then have a million 30-year olds infected, you've got 100 deaths. So while it looks like a low probability per person, in our population that's still a lot of deaths that are preventable," he said.

Professor Collignon "wouldn't promote [AstraZeneca] to that age group" with Pfizer and Moderna likely to fill supply holes within the next four months.

"[But] if somebody who's 35 wants to get the vaccine, and they're aware of the risk of these clots, that's their decision," he said.

He said hospitalisations and deaths were obvious and accurate data, but the threat of 'long-Covid' - a post-viral condition lingering well after the initial infection - was a genuine consideration for young people.

"I think we're underplaying the benefits by just looking at ICU admissions," he said.

Australia's rollout was rocked in April by ATAGI advice making the Pfizer jab the "preferred" vaccine for people aged under 50, later rising to 60.

The fact AstraZeneca remained open to anyone above 18 who consulted their GP was lost in a flurry of hastily-arranged press conferences.

The government's messaging since, using the development to explain Australia's sluggish rollout then downplaying its significance, hasn't helped.

Its claim to be guided by medical advice was also dented by a frustrated Scott Morrison hanging ATAGI out to dry last week, revealing "constant appeals" to change its advice.

Infectious diseases expert Bill Bowtell warned the "mixed messaging" had damaged trust in AstraZenca.

"[It] really put a lot of concern out there about [whether] AstraZeneca was safe, far in excess of the evidence or the information," he said.

In a sign authorities were increasingly anxious to reach young people, NSW Chief Health Officer Kerry Chant took questions from TikTok influencers on the importance of vaccination this weekend.

And Professor Bowtell, who was at the forefront of Australia's information campaign on HIV, said more targeting of young people through their preferred mediums was needed.

"The methods by which young people communicate are not free to air television and legacy media. It's not pitched in a way that makes sense [to them]," he said.

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