Introduction by Croakey: Amid widespread concern and confusion about the changing COVID vaccination situation and headlines about a “bungled” vaccine rollout, we need clear, calm messaging that is unpolluted by political agendas.
This need is likely only to grow, given that the Australian Technical Advisory Group on Immunisation (ATAGI) has made clear that its latest vaccination recommendations, issued last night, may change again.
This could happen if evidence emerges of community transmission or there are significant COVID-19 outbreaks, or if other evidence emerges around vaccine safety.
It is worth reading the full ATAGI statement explaining the rationale behind its latest recommendations (noting that advice is still to come for some specific groups, such as those who are pregnant and those who have thrombosis risk factors).
In summary:
- At the current time, use of the Pfizer vaccine is preferred over AstraZeneca vaccine in adults aged under 50 years who have not already received a first dose of AstraZeneca vaccine. This is based both on the increased risk of complications from COVID-19 with increasing age (and thus increased benefit of vaccination), and the potentially lower, but not zero, risk of the thrombosis thrombocytopenia syndrome (or TTS) with increasing age. This is a rare, new syndrome which has been reported after administration of the AstraZeneca vaccine. It may be caused by this vaccine. The condition involves blood clots (occurring in sites like the brain or abdomen) together with low platelet levels.
- The AstraZeneca vaccine can be used in adults aged under 50 years where the benefits are likely to outweigh the risks for that individual and the person has made an informed decision based on an understanding of the risks and benefits.
- People who have had their first dose of the AstraZeneca vaccine without any serious adverse effects can be given their second dose. This includes adults under 50 years of age. People who have had blood clots associated with low platelet levels after their first dose of the AstraZeneca vaccine should not be given their second dose.
- The Department of Health should further develop and refine resources for informed consent that clearly convey the benefits and risks of the AstraZeneca vaccine for both immunisation providers and consumers of all ages.
ATAGI also had this pointed advice: “Where possible, onshore manufacturing of alternative safe and effective vaccines should be considered.”
The statement was helpfully explained by ATAGI’s co-chair Professor Allen Cheng in a Twitter thread published late last night and republished here with permission. He also links readers into useful resources.
Allen Cheng writes:
Like with all medical treatments, when we have a choice we need to consider the risks and the benefits. In this case we’re thinking about the risk of a side effect due to vaccination and the benefit of a reduced risk of COVID.
A rare but serious clotting disorder (thrombosis with thrombocytopenia) has been reported after the AstraZeneca vaccine. One case has been reported in Australia to date from about 420,000 AstraZeneca vaccine doses which ATAGI reported on Good Friday.
While DVTs (deep clots) in general are common and don’t seem to be increased following vaccination, emerging evidence suggests that this unusual disorder is probably caused by vaccination.
However, it appears to be quite rare – UK data suggest that it is in the rate of 1 case per 200,000 to 250,000 vaccines. Other estimates put the risk as somewhat higher, but still pretty rare.
While there are more cases reported in younger people and women, it isn’t clear if this just reflects the populations that received the vaccine first (especially healthcare workers).
The other side of the equation is the potential benefit of the vaccine in preventing COVID.
The risk of severe COVID is strongly linked to age. The risk of death from COVID rises roughly three-fold for every 10 years of age. A 50-year-old is roughly 10 times more likely to die from COVID than a 30-year-old.
So the benefit of getting vaccinated (and not getting COVID) is much higher for older people than younger people.
Thus, the benefit in preventing COVID through vaccination is greater with age, and risk of this clotting condition possibly decreases with age.
So how did we come up with 50 years? And why did the UK pick 30 years as a threshold?
If there was a lot of COVID about, then the benefit in preventing COVID would outweigh the risk for almost all adults, except for very young adults. This is pretty much the situation in the UK at the moment.
In Australia, we don’t have COVID in the community at the moment, but we recognise that the risk of incursion is ever present. So the balance of the risks and benefits are different.
This is helpfully explained by this infographic from Cambridge (for reference, the “low exposure risk” corresponds roughly to the risk during the second wave in Victoria)
Caveats
There are a few caveats here. If we could work out who did and who didn’t get this clotting condition, we might be able to advise younger people better about their personal risk.
If we had a large outbreak, then this risk benefit analysis would change and we’d have to reconsider this advice. The risk benefit balance would also be different in countries with even larger outbreaks than the UK.
We also carefully used the word “prefer” (Pfizer over AstraZeneca) in younger people. We respect patient autonomy – that people have a choice about the vaccines and treatments they get.
If a younger person said that they were happy to take a 1 in 200,000 risk of clotting for the benefit of getting protected from COVID earlier, then as long as this was an informed decision, we should respect that choice.
But if you get severe persistent headaches or other unusual symptoms between 4 and 20 days after vaccination, seek medical attention. (This is different to the common side effects after vaccination, which usually only last a day or so)
The other obvious question is about alternatives to AstraZeneca. I’m not privy to the discussions, but I do know that the Australian Government have been in constant communications with vaccine manufacturers.
It’s no secret that there is global competition for available vaccines, and we have secured enough Pfizer for 40 percent of the population over the remainder of the year (Note from Croakey: the Government announced today that another 20 million Pfizer doses would be available in the final quarter of 2021).
We have access to some more vaccine via COVAX, and Novavax hopefully coming later in the year subject to regulatory approvals and supply.
There’s no question that this decision will slow things down – having onshore capacity to produce vaccine is very valuable.
So over the next few days, Commonwealth and state governments will be working out how the program will look in the coming weeks and months. But because we’re thankfully not dealing with ongoing COVID outbreaks, we can make this choice to take a safer path.
Note from Croakey: More detail about the roles and membership of ATAGI can be found here.
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