Australia's drug regulators are holding urgent meetings after European authorities confirmed a link between AstraZeneca's COVID-19 vaccine and blood clots.
The European Medicines Agency (EMA) has listed blood clots as a very rare side effect of the vaccine.
They found women taking contraceptive pills and people under 60 were at higher risk of developing the rare side effect.
"We can now say it is clear that there is an association (of the brain blood clots) with the vaccine," Marco Cavalri, chair of the vaccine evaluation team at the EMA told Italian newspaper Il Messaggero.
"However, we still do not know what causes this reaction."
The United Kingdom has restricted the AstraZeneca vaccine for people under the age of 30 due to these risks, however, Australian Prime Minister Scott Morrison says it's still too early to say whether Australia would follow.
Morrison says there's nothing to suggest the national vaccine rollout would be affected at this stage, particularly because the early phases of the rollout were focussed on older members.
Australia's Chief Medical Officer Paul Kelly says Australian regulators are now considering the findings.
"The recommendations will be brought to the table today and look at the Australian context," he said on Thursday.
"The AstraZeneca vaccine is effective and very safe for most people. This is an extremely rare event which appears to be associated with that particular vaccine in some people - four per million.
"The benefit is that the vaccines are very effective at preventing COVID illness and can be severe and lead to deaths, particularly in older people."
Federal Opposition Leader Anthony Albanese says the advice on AstraZeneca highlighted the Australian government's failure to secure vaccine deals with other suppliers.
"The federal government should have secured more deals. There is no deal for Moderna. There is no deal for Johnson and Johnson.
"Scott Morrison's always out there happy to blow his trumpet about how everything is going. Australians are worried. Australians deserve better than a 'she'll be right mate' approach."
Australia is currently using two vaccines - the Pfizer-BioNTech and AstraZeneca, however, Pfizer-BioNTech is still the only vaccine approved in New Zealand.