Australia's vaccine rollout hit a hurdle overnight. Here's what we know.

On Thursday evening, Prime Minister Scott Morrison gave a snap press conference in which his Government announced a significant change to Australia's COVID-19 vaccine rollout plan.

Based on advice from The Australian Technical Advisory Group on Immunisation, it's now recommended that Australian's under the age of 50 receive the Pfizer vaccine.

The change comes in the wake of a small number of global reports of blood clotting among recipients of the AstraZeneca vaccine — which is currently the only other COVID-19 jab approved for use in Australia.

So what's the risk posed by the AstraZeneca vaccine, and how will the new recommendation affect Australia's vaccine rollout? Let's take a look.

OK. So, what's changing exactly?

The Government has issued three new recommendations based on advice provided by The Australian Technical Advisory Group on Immunisation (a group of experts on vaccines, epidemiology and vaccination programmes):

• Pfizer is preferred over AstraZeneca COVID-19 vaccine in adults aged under 50 years;
• The AstraZeneca vaccine should only be given as a first dose to adults under the age of 50 where the benefit clearly outweighs the risk for that individual;
• People who have had their first dose of COVID-19 Vaccine AstraZeneca without any serious adverse effects can be given their second dose.

"It's a rare event, but it is serious"

Chief Medical Officer Professor Paul Kelly on the government's decision to axe the AstraZeneca vaccine for Australians aged under 50 due to blood clot fears. pic.twitter.com/x2cGTEqOMF

— Sunrise (@sunriseon7) April 8, 2021

The Prime Minister stressed that these are recommendations for vaccine providers and patients, not mandates. And he encouraged people to discuss the issue further with their doctor.

Why is the AstraZeneca vaccine no longer preferred for younger Australians?

There have been a small number of reports around the world of blood clots occurring among recipients of the AstraZeneca vaccine, including one man who was hospitalised in Melbourne.

These clots can be fatal in up to 25 per cent of people who develop them. Nineteen vaccine recipients in the United Kingdom, for example, have died.

There is still no conclusive evidence that the vaccine is directly causing the clots (as opposed to other underlying factors). But as an extreme precaution, several countries have adapted their vaccine rollouts to favour other jabs for those apparently most at risk.

Australia has now followed suit.

Why do the changes only apply to people under 50?

Professor Brendan Murphy, Secretary of the Australian Department of Health, explained that preliminary data seems to show that these incidents of blood clotting occur mainly in younger people, for whom the risk of severe COVID-19 infection is not as high.

"That, there, is a basis to have a preferred recommendation for those under 50," he told media on Thursday. 

"I want to reiterate that we are strongly encouraging those 50 and over to take up the AstraZeneca vaccine. It is a highly effective vaccine at preventing severe COVID. 

"The risk [of clotting] is extraordinarily low. I've had my first dose, I'll have my second dose. It is a vaccine that is very, very effective."

What actually is the risk of blood clots with the AstraZeneca vaccine?

As Professor Murphy stressed, incredibly low. 

In the United Kingdom, 79 cases of blood clotting issues were reported among 20 million vaccine recipients. That's a chance of about 0.0004 per cent, or one in 250,000.

Either way, experts are stressing the risk is minute. Particularly, when compared to other medicines. 

Take the combined oral contraceptive pill, for example. Global studies have placed the incidence of blood clotting for that common medicine at between 5-12 per 10,000 people. 

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Matthew Linden, Associate Professor of Haematology and Transfusion Medicine at The University of Western Australia, said the incidents of blood clots detected in people recently vaccinated with the AstraZeneca jab "is not unique to the vaccine".

"Many commonly used medicines also carry a risk of blood clotting. This can occur when a person’s immune system mistakenly mounts a response against their own blood platelets, upsetting the delicate balance of blood," he said.

"While serious, it is important to note that the risk is rare and for more than 99.999% of people it will not be a concern. Therefore, the rationale for getting vaccinated in the context of a global pandemic remains abundantly clear."

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So, why has the Australian Government changed its recommendations?

Unlike Europe and the UK, where COVID-19 remains widespread throughout the community, Australia has no community transmission. 

While the need to complete our vaccine program is still an urgent one (both from a health and economic point of view), Prof. Murphy explained that it's precisely because Australia is in such a fortunate position that we can afford to take such "highly precautionary" measures.

The stakes simply aren't as high as countries still battling thousands of new diagnoses daily.

How will the change affect Australia's vaccine rollout?

First, a quick recap. Australia will be relying on three vaccines for its COVID-19 vaccination program:

• Pfizer's vaccine, which is manufactured overseas and of which we've secured 40 million doses (the deal was upped overnight from the original order of 20 million).
• Astra-Zeneca's, the bulk of which will be manufactured in Melbourne (guaranteeing supply).
• Novavax, of which we've secure 50 million doses. Although, this jab is still pending approval by Therapeutic Goods Administration.

Australia is still in Phase 1B of its rollout plan, which includes Australians over 70, health care workers and emergency services. 

The bulk of Australians affected by the new recommendations — that's up to 16 million people aged between 16-50 —are in phase 2b and 3, so the Government has some breathing room to ensure sufficient supply of the other jabs.

Prof. Brendan Murphy, Secretary of the Department of Health, said the Government is now reviewing the purchases Australia has made.

As well as the bolstered Pfizer supply, Australia is hoping to lean on Novavax. The TGA approval process is looking promising and, pending the outcome of that, the Government has flagged delivery could occur in the third quarter of 2021.

Still, it seems likely that the new recommendations will further slow down the already delayed rollout.

Indeed, when asked if all Australians will be vaccinated by the end of the year, as was initially promised, the Prime Minister refused to answer. In fact, he doesn't have a rough timeline at all at this stage.

"We have to take the time to assess the implications [of the new recommendations] for the programme," he said. "And when we've done that, well, we may be able to form a view, but I don't think anyone should expect that any time soon. This will take some time to work through the implications."

Feature image: Getty.