The AstraZeneca vaccine is being blamed for causing blood clots that have placed a 66-year-old Townsville man in ICU and an elderly Tasmanian man in hospital.
Queensland's chief health officer Dr Jeanette Young revealed the 66-year-old's condition has been directly linked to being vaccinated against Covid-19.
"The TGA, I understand, will announce later today a case of thrombosis following an AstraZeneca vaccination in a 66-year-old gentleman in Townsville," she said.
"He has been admitted to the ICU.
"TGA has confirmed that his illness is a direct result of the AstraZeneca vaccine."
A statement from the Tasmanian Department of Health has said their 70-year-old patient is in a stable condition in hospital.
"The patient, a 70-year old man, reported symptoms seven days after receiving the vaccine. He is currently in hospital receiving treatment and remains in a stable condition," the statement read.
"Information about the case was notified to the Therapeutic Goods Administration (TGA) for assessment, including to determine whether the case is linked to vaccination.
"The TGA has today confirmed that this case (together with four cases from other states) has been assessed as TTS, likely to be linked to the AstraZeneca Covid-19 vaccine."
Dr Young said the Queensland patient had received an initial AstraZeneca jab on March 30 and soon afterwards had a reaction which worsened over time.
"He received the first dose of the vaccine, on the 30th of March, subsequently developed some abdominal pain and presented to the Townsville Hospital, where he was admitted and tested," Dr Young said.
"It's now been confirmed that he is most likely developed that syndrome."
The incident should not deter people from being vaccinated against Covid-19, said Health Minister Yvette D'Ath.
"Vaccine confidence is really important. We want as many Australians and Queenslanders to get vaccinated," she said.
"We know that is really important to protect our community … and we will continue to act on the advice of the TGA."
The news comes as Queensland tightens its borders with NSW following two locally acquired coronavirus cases in Sydney.
Anyone arriving from NSW who has been to one of 19 "hot spot" venues will be sent to hotel quarantine from early Friday morning.
D'Ath said from 1am Friday, anyone arriving in Queensland who had been to any of the 19 venues in NSW, where the two positive cases had visited, will spend two weeks in hotel quarantine.
She said police would vet arrivals and it was a "reasonable" and "proportionate" measure.
"Anyone who identifies as having gone to those venues will quarantine for 14 days," D'Ath told reporters.