The AstraZeneca coronavirus vaccine is no longer recommended for people aged under 60 after new expert immunisation panel advice.
Health Minister Greg Hunt has confirmed new recommendations from the Australian Technical Advisory Group on Immunisation about extremely rare but serious blood clots.
"We accept the advice and accept that Pfizer is the preferred vaccine for under 60s. AstraZeneca is recommended for over 60s," he told reporters in Canberra.
For people who have had a single dose of AstraZeneca, health authorities have given the green light for the second jab.
The decision puts further strain on the federal government's vaccine rollout which will now have to rely more heavily on imported Pfizer doses.
Access to Pfizer will be expanded to all Australians aged 40 to 59.
AstraZeneca was considered the backbone of the immunisation strategy until ATAGI recommended in April the vaccine be used for over-50s.
Millions of doses of AstraZeneca are being produced in Melbourne but Australia has no capacity to build mRNA vaccines like Pfizer and Moderna.
Two people who received AstraZeneca have died in Australia after developing blood clots with both in their 50s.
As of last week, more than 3.6 million doses of AstraZeneca have been administered nationwide since the rollout kicked off in February.
Treasurer Josh Frydenberg said the government was seeking access to other vaccines.
"Obviously our success as an economy to keep the momentum going will depend on our ability to suppress the virus," he told reporters in Canberra on Thursday.
"That means following the health restrictions, but it also means rolling out the vaccine. That is what we are seeking to do as more supply becomes available."
Australian Associated Press