Australians aged 30 and older are now eligible for a fourth dose of the COVID-19 vaccine.
The decision comes after recommendations from the Australian Technical Advisory Group on Immunisation (ATAGI) were accepted by the government on Thursday.
While confirming the eligibility expansion, Health Minister Mark Butler announced 7.4 million people can get their fourth dose from July 11.
Here's where things are currently at.
Who is eligible for a fourth COVID jab?
ATAGI specifically recommended the shot for people over 50, while people aged 30 to 49 may choose to have a fourth dose.
Mr Butler said there was "a strong case" for Australians under 65 to receive the additional booster shot.
He also said there was an "open question" about whether young, healthy people needed it.
Under the previous guidelines, the fourth dose was available to people aged over 65, aged care residents, Aboriginal and Torres Strait Islander people aged 50 and older, people with a disability, the immunocompromised and anyone over 16 with a medical condition that increases the risk of severe COVID-19.
What if I'm under 30?
ATAGI did not support making the fourth dose available to healthy adults under the age of 30 years as it was not clear whether the benefits outweighed the risks in this population group.
When can I get the fourth jab?
The fourth dose will be available to those who are newly eligible from Monday, July 11.
How long do I need to wait after my last dose?
But if you've had COVID-19 since receiving your booster shot, you have to wait until three months after you acquired the infection.
Which vaccine should I get for my fourth shot?
Pfizer and Moderna — both of which as mRNA vaccines — are ATAGI's preferred vaccines.
But the AstraZeneca vaccine can be used when someone can't have an mRNA vaccine for medical reasons or if they decline one.
Novavax is also approved to be administered as a fourth dose, but only if no other vaccine is considered suitable for that person.
How many people have had three or more doses?
Almost 14 million people in Australia aged 16 and over have received three or more doses of COVID-19 vaccine.
That works out to be about 70.6 per cent of people currently eligible for the booster shot, according to the latest federal update, which takes in data from the Australia Immunisation Register collected up until 11.59pm on Tuesday.
How many people have had four or more doses?
According to the latest federal update, more than 2.4 million.
Of those, more than 2.1 million are people aged 65 and older.
The number of people eligible for a winter dose changes from day to day, because people become only eligible for the winter booster four months after they received their third dose.
Why weren't fourth doses recommended for everyone before?
In a statement, ATAGI said there was "insufficient evidence of the benefits of an additional booster dose" to recommend them for people who don't fall into those categories listed above.
"Protection against infection wanes after the first booster dose," its statement says.
"However, protection against severe disease (rather than all infection) is relatively well maintained, especially in young healthy populations."
Essentially, ATAGI is saying that while people outside those four groups may get sick from COVID-19, there's a lower risk they'll become severely ill from the virus.
