Graph reveals reason behind AstraZeneca fears for under 30s

Nick Whigham
·Assistant News Editor
·4-min read

Questions have emerged about the trade-offs involved with the AstraZeneca Covid vaccine in healthy people under the age of 30, with research finding it could carry more risk than the virus itself. 

The United Kingdom has pumped the brakes on giving the Oxford University AstraZeneca jab – the primary vaccine in Australia's rollout – to those in their 20s with no underlying health conditions. 

Overnight the country's Joint Committee on Vaccination and Immunisation (JCVI) said those in that category should be offered an alternative jab due to a "vanishingly" rare side effect of blood clots in the brain.

Although vanishingly small, there is concern over deadly blood clots. Source: Getty
Although vanishingly small, there is concern over deadly blood clots. Source: Getty

Because that particular cohort is at such low risk of mortality from Covid-19, an alternative vaccine makes statistical sense, said JCVI chair Wei Shen Lim.

"We are advising a preference for one vaccine over another vaccine for a particular age group, really out of the utmost caution, rather than because we have any serious safety concerns," he said at a briefing overnight.

With more than half the country already receiving a jab, Dr Lim said people should continue to have a second dose of the AstraZeneca shot if they had received a first dose.

Government graphs shows benefit analysis of the jab 

The UK's MHRA medicine regulator published slides overnight showing a breakdown of the risk assessment that underpins the caution. 

In one scenario, plotted in an environment with low community transmission (seen in the image below) the potential risks of the vaccine for those in there 20s was actually greater when compared with the likelihood of being admitted to the ICU with Covid-19. 

In a low transmission environment, healthy 20-year-olds have an overall very small risk factor from coronavirus. Source: Uk Gov
In a low transmission environment, healthy 20-year-olds have an overall very small risk factor from coronavirus. Source: Uk Gov

While the graph is based on community spread of about 2 cases per 10,000 people, the benefits of the vaccine outweigh the minute risk of blood clots in an environment with greater community spread, and therefore more chance of suffering from severe coronavirus symptoms. 

The same scenario with 20 cases per 10,000 meant the benefits of the vaccine exceeded the small statistical concerns around blood clots.

Cases of ICU admissions prevented by the vaccine change the cost/benefit analysis in a high spread environment. Source: UK Gov
Cases of ICU admissions prevented by the vaccine change the cost/benefit analysis in a high spread environment. Source: UK Gov

In the UK, 19 people have died with their deaths linked to blood clots after receiving the AstraZeneca vaccine, with three of those people under the age of 30.

Vaccine deaths can not be dismissed

Australian regulators face difficult questions as the country's vaccine rollout starts to ramp up, experts say.

“Drugs and vaccines are all about risks and benefit and that changes based on country,” says Professor Nikolai Petrovsky, a vaccine expert from Flinders University. 

“It’s wrong to dismiss anything that might kill any young person,” he told Yahoo News Australia.

“You’d be potentially killing more people than you’d be saving ... That’s real data,” he said, referring to the UK analysis.

Given Australia has no known community spread of the virus, Prof Petrovsky said the overall benefit of the vaccine does not currently outweigh the potential risks in many cases. 

"The risks of this side-effect are likely to be the same globally, but obviously what is different is the calculation of the benefits because that will be dependent on the amount of Covid-19 circulating."

He expects Australia might do something similar to what Germany announced last week and restrict use of the AstraZeneca jab to the elderly, while Belgium has also paused its AstraZeneca rollout for those under 56.

However, given the Oxford jab makes up a vast majority of our vaccine supply, the federal government is in a very tricky situation.  

"That's something they've been criticised for, for some time now – putting all their eggs in one basket," Prof Petrovsky said. 

The federal government has also come under fire for a lack of transparency around the rollout so far and Prof Petrovsky called on the government to "publicly explain what the benefits are so people can make their own judgements".

Australia to consider next move with AstraZeneca

Chief Medical Officer Paul Kelly said Australian regulators were considering the findings.

"The recommendations will be brought to the table today and look at the Australian context," he said on Thursday.

"The AstraZeneca vaccine is effective and very safe for most people. There is this extremely rare event which appears to be associated with that particular vaccine in some people - four per million.

"The benefit is that the vaccines are very effective at preventing Covid illness and can be severe and lead to deaths, particularly in older people."

Meanwhile, Prime Minister Scott Morrison said it was too early to say whether Australia would follow other countries adding warning labels to the AstraZeneca vaccine or give those under 30 a different drug.

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