A new study of more than one million Covid-19 vaccine recipients has concluded a rare blood clotting side effect is as likely to occur from a Pfizer jab as the much-maligned AstraZeneca vaccine.
In a paper pre-released in The Lancet, researchers from the UK, Spain and the Netherlands said both jabs have a "similar" incident rate of thrombosis.
"In this study we have found the safety profiles of ChAdOx1 (AstraZeneca) and BNT162b2 (Pfizer), an mRNA-based vaccine, to be broadly similar," the paper explained.
The study of Spanish patients also found blood clots are more common in people who test positive for Covid-19 than those who have received either jab.
While the paper is not yet peer reviewed, it is an alarming development that will put into question the narrative around the AstraZeneca vaccine in Australia, where confidence in the jab plummeted earlier in the year following the reporting of fatal cases of blood clotting.
Mixed messaging around the vaccine has led to hesitancy at a time when the nation, particularly NSW, needs to reach a high level of vaccination to fend off surging rates of the highly-infectious Delta variant.
While Chief Medical Officer Paul Kelly has repeatedly stressed the benefits of the AstraZeneca jab outweigh the risks, there has been conflicting advice from other health authorities, notably Queensland's Chief Health Officer Dr Jeannette Young.
When Prime Minister Scott Morrison urged under 40s to seek advice on the AstraZeneca jab last month, Dr Young said she "genuinely did not understand" why Mr Morrison would make such an announcement.
"I do not want under-40s to get AstraZeneca," she stressed, saying there was minimal death in young Australians from Covid.
As cases of blood clotting arose earlier in the year, believed to be thrombosis with thrombocytopenia syndrome (TTS), the Australian Technical Advisory Group on Immunisation (ATAGI) advised against under 60s receiving the AstraZeneca jab.
Such mixed messaging has led to an increase in people eligible for the jab holding out for the scarce Pfizer vaccine, including those who have had one AstraZeneca jab.
Weighing up the heightened risk with Delta outbreaks, ATAGI has since changed its advice, telling over 18s they can seek GP advice on the AstraZeneca.
Experts fear lasting damage from mixed messaging
Professor Greg Dore, an infectious diseases expert at UNSW's Kirby Institute, told the Sydney Morning Herald Australia will "look back on anti-AstraZenecism as one of the greatest public health failings in many years".
“Even though we’ve seen many young people coming forward for AstraZeneca, many more older people are still ‘waiting for Pfizer’ due to irreparable damage by some in the medical profession and other commentators," he said.
Dame Sarah Gilbert, the vaccinologist who co-developed the AstraZeneca jab, told the publication she feared people are "too worried" after receiving mixed messages.
"I think the problem is the messaging around the vaccination, because if you’re telling people at some stage, ‘oh you shouldn’t have this vaccine, it’s probably not the best thing for you’ and then you want to change that message and say ‘oh, no we’ve changed our mind, it is good’, I think that makes it difficult for people who are considering whether to get vaccinated and when to get vaccinated," she said.
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