A man is being treated in a Melbourne hospital for an "extremely rare" blood clot condition after receiving the AstraZeneca COVID-19 vaccine.
Chief Medical Officer Michael Kidd confirmed earlier media reports on Friday, stressing it is not clear whether the illness is linked to the man's vaccination but that health authorities are taking the case "very seriously".
The man is in Box Hill Hospital, in east Melbourne, after receiving the vaccine on 22 March, according to the ABC.
It is the first blood clot case in Australia, although earlier cases in the United Kingdom and Europe prompted a temporary pause in a number of countries until the EU medicines regulator declared the AstraZeneca vaccine "safe and effective".
A causal link with the AstraZeneca vaccine is yet to be established.
Professor Kidd said he wanted to reassure Australians the risk of contracting COVID-19 was "far greater" than contracting the "very small potential risk" of a rare blood clotting disorder as a side effect.
"I remind anyone receiving a vaccination over the coming few days that these instances of serious clotting disorders are extremely rare and have occurred in only a very small number of cases," he said.
"At this time, the risk of serious disease and death from COVID-19, if we experience another severe outbreak, especially among older Australians and those with severe health conditions, is far greater than the very small potential risk of a very rare clotting disorder associated with the vaccine," he said.
The Australian Technical Advisory Group on Immunisation (ATAGI) COVID-19 Working Group are meeting on Friday evening to discuss further advice on the AstraZeneca vaccine.
Professor Kidd said he will be outlining further information on Saturday, and he will also be talking to "colleagues in the European Union and United Kingdom over the coming few days".
The blood clot case will also be examined by the Therapeutic Goods Administration (TGA) on Saturday to determine whether it could be linked to the AstraZeneca vaccine.
Professor Kidd said expected side effects from either the Pfizer or AstraZeneca jab could include fever, sore muscles, tiredness and headache and that such symptoms could start about 24 hours after receiving the vaccine and last one to two days.
"These are expected and not of concern unless severe or persistent," he said.
The most concerning symptom would be severe anaphylaxis, which is why people are monitored for about 15 minutes after receiving the vaccination - and longer if they have a past history of serious allergic reactions to vaccines.
He said people should be particularly alert to severe and persistent headaches that occu between four and 20 days after the vaccination, which "are different to your usual pattern of headaches" and do not settle with paracetomol or other over-the-counter painkillers.
"If you receive the AstraZeneca vaccine and you experience symptoms of severe, persistent headache or other worrying symptoms, four to 20 days after the vaccine, you should seek medical advice as soon as possible," he said.
"Anyone attending their general practitioner or hospital should let the treating doctor or other clinician know the details of which vaccination they have received and when."
It comes as Queensland and NSW celebrated doughnut days with no new community cases of COVID-19, as concerns continue to be raised about the federal government's managed rollout of vaccines.
Eight new cases have been identified in Queensland - seven in hotel quarantine and one historical case, which is believed to be the missing link to one of two clusters in Greater Brisbane.
Meanwhile, NSW recorded its second consecutive virus-free day after a case linked to the Queensland outbreak was diagnosed in Byron Bay earlier in the week.
However, concerns continue to surface over the rollout of vaccines, with Queensland almost out of the Pfizer inoculation and unsure when it will receive its next delivery.
The Pfizer vaccine has been used predominantly to vaccinate frontline healthcare and quarantine workers.
Additional reporting: AAP
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