A 53-year-old South Australian man is being treated in intensive care for blood clotting that health authorities say is linked to the AstraZeneca vaccine.
It is the first case recorded in the state, with 150,000 South Australians so far receiving the AstraZeneca jab.
Authorities are also investigating a second case of blood clotting in an 87-year-old woman who received the AstraZeneca vaccine last month.
South Australia's Chief Public Health Officer, Nicola Spurrier, said the man was in a "very serious condition" after receiving his first dose on May 4.
He was admitted to hospital with severe abdominal pain on Tuesday.
SA Health received confirmation from the Australian Technical Advisory Group on Immunisation (ATAGI) that his clotting was linked with the AstraZeneca vaccine last night.
She said the case was "obviously of great concern but not unexpected".
The 87-year-old woman received her vaccine on April 28 and was admitted to hospital on May 11.
She is in a stable condition, Professor Spurrier said.
One fatality linked to AstraZeneca vaccine
The two cases bring the total Australian reports of cases of thrombosis with thrombocytopenia syndrome (TTS), including suspected cases, following the AstraZeneca vaccine to 24.
The Therapeutic Goods Administration (TGA) said 21 other linked cases were out of hospital, while another two were in hospital.
There has been one fatality, a 48-year-old woman from New South Wales.
About 2.1 million AstraZeneca jabs have been administered in Australia.
Immunisation Coalition chairman Rod Pearce said there appeared to be about 11 blood clot cases per 1 million people vaccinated, which was about the same number that could be anticipated going on overseas trends.
"It's important we keep rolling out our vaccine program because in the long run it's going to be our fight against the disease, which is more important than managing the side effects," Dr Pearce said.
Professor Spurrier said people who have had a vaccine should watch for a severe persistent headache or severe abdominal pain between four and 28 days after receiving a dose.
Her husband, physiotherapist David Spurrier, received the AstraZeneca vaccine last Thursday.
She said he was "not getting too stressed about it" but "keeping a bit of an eye on" possible blood clot symptoms.
"Just being aware if there was anything like that that he would need to go and get a health check," she said.
Professor Spurrier also announced a new case of COVID-19 reported in hotel quarantine, bringing South Australia's total to 747.
Four new cases were reported on Tuesday.
