People who actually catch coronavirus are nine times more likely to develop these particular types of blood clots than people who get the AstraZeneca vaccine.
"When we look at what is happening with people who have been admitted to hospital throughout the whole pandemic, 16 per cent of people have had a clot of some sort related to their COVID disease," Chief Medical Officer Paul Kelly said.
"So clotting is a feature of COVID. It also happens to be a feature, very rarely, of this AstraZeneca vaccine."
Professor Kelly urged people who were eligible for the vaccine to come forward to get a shot.
The benefits of the AstraZeneca vaccine outweigh the risk of potential fatal blood clots, Professor Kelly said.
"The risk of severe COVID infection increases with age, whereas the risk of the clots decreases with age," he said.
"We are in a very unusual situation here in Australia at the moment, with no community transmission."
But he warned Australia's situation was only temporary.
"The chances of being infected will increase, so being vaccinated is a protection not only for yourself, but also for the people you care for," he said.
"That is why we have a vaccination program."
Professor Kelly warned against jumping to conclusions in connection with the death of a 48-year-old woman who died days after receiving the coronavirus vaccine.
He said the Therapeutic Goods Administration (TGA) has a lot of information to look through.
"It is true she had the AstraZeneca vaccine a few days before she became ill," he said.
"Whether those two events are related is a matter for those experts that will be meeting today."
She had "severe chronic disease issues", the Chief Medical Officer said.
"I do know she did have several chronic disease issues, but whether that was why she was vaccinated or whether it was because she was one of the workers in those categories, I do not know that information," Professor Kelly said.
Professor Kelly noted it has only been one year since the very first people received the coronavirus vaccines in clinical trials.
"There are many unknowns at the moment in terms of the vaccine, one of them is about the duration of effectiveness," he said.
"It is likely that we will know sometime in the next six months to one year."
- Date Fri, 16 Apr 2021
- Outbreak Covid-19
- Category World
- View 775