Renowned infectious diseases expert Tony Cunningham cannot understand why older Australians are baulking at the AstraZeneca vaccine.
More than a quarter of Australians aged 60 and over are yet to receive their first jab, while only 30 per cent are fully vaccinated against COVID-19.
The AstraZeneca vaccine has caused a blood-clotting disorder in very rare cases, with death a one-in-a-million risk.
Professor Cunningham, an infectious diseases physician who has served on numerous international expert vaccine panels, says that paled against the high-risk coronavirus posed for people aged over 60.
"If you're over 80, you've got a 15 to 20 per cent chance of dying if you get COVID-19 and you're matching this up against one in a million," he told a business forum on Friday.
"I just cannot understand why people would not protect themselves."
Thrombosis and Thrombocytopenia Syndrome, the clotting disorder caused by AstraZeneca, occurs once in every 58,000 jabs given to over-60s.
Under-60s have a slightly higher chance of developing TTS, with one case recorded in every 38,000 jabs given in Australia.
Thirteen people, including a woman aged 38, have died in Sydney's current outbreak, out of 2980 cases.
"I've got scared people in their 20s and 30s coming to me (asking me about AstraZeneca)," Prof Cunningham said.
"I'm saying to my friends and relatives: 'please, please immunise as quickly as you can and protect yourself against a virus that might end up with you in ICU."
Professor Sarah Palmer, also speaking at the Western Sydney Business Connection webinar on Friday, said people weighing vaccination benefits and risks should also consider the high rate of COVID-positive people developing "long COVID".
The syndrome - causing fatigue, brain fog, muscle weakness and coughing for up to a year after diagnosis - was present in some form for 30 per cent of positive cases, she said, citing US data.
"It's not a rare phenomenon," the infectious diseases expert said.
"This virus can damage heart, lung and brain tissue. It can cause long-term health problems."
Both experts, who co-direct the Westmead Institute of Medical Research's Centre for Virus Research, dismissed as "fake news" so-called horror stories spreading on social media about 30,000 dying in the US after receiving a vaccine.
Prof Cunningham said he, Prof Palmer, their colleagues and NSW Chief Health Officer Kerry Chant had all been vaccinated.
"That's a lot of very knowledgeable people who know a lot about this, who have looked at all the data and thought: 'My gosh, I'm going to protect myself, my family and my community by being immunised'," he said.
One in every seven Australians is fully vaccinated. Thirty-two per cent have had at least one shot.
The 12-millionth COVID vaccine was administered on Friday.
Australian Associated Press