As of Monday, an extra 7.4 million Australians will be eligible for a fourth COVID-19 vaccine booster shot.
On Thursday, the Australian Technical Advisory Group on Immunisation (ATAGI) recommended everyone over 50 have a fourth dose.
And while it didn't go as far as to recommend people aged 30-49 have a fourth dose, ATAGI said they can if they want to.
It also reduced the length of time between booster shots from four to three months.
Let's unpack what it means for you.
What vaccine can I get?
People under 18 can have the Pfizer vaccine as a booster.
The Pfizer and Moderna vaccines are approved for booster shots for people aged 18 and older.
The Federal Department of Health says while not preferred, the AstraZeneca and Novovax vaccines can be used as a booster shot when someone can't have an mRNA vaccine for medical reasons, or if they prefer not to have a mRNA vaccine.
- AstraZeneca makes a viral vector vaccine
- Novavax makes a protein-based vaccine
- Pfizer and Moderna make mRNA vaccines
Should I mix and match my boosters?
There doesn't seem to be much point.
Senior lecturer of public health at University of Technology Sydney Jane Frawley says while there was some research earlier in the pandemic suggesting there were added benefits of having an mRNA booster after having two initial doses of AstraZeneca, there's not much difference when it comes to fourth doses.
That's because a lot of people will have had either Pfizer or Moderna for their third shot — and both of those are mRNA vaccines.
Dr Frawley says it's best to just go with what's most convenient.
"We know they both work really well," she said.
Head of vaccine and immunisation research at the Doherty Institute Terry Nolan agreed.
"There's no point and no argument to mix and match," Professor Nolan said.
He said while there were subtle differences between Pfizer and Moderna, there was "no convincing evidence" to suggest mixing them up.
"I think the bottom line is that there isn't a difference between the two," he said.
"There's a difference between Novovax and the mRNA vaccines – but in the way they're made, not in effectiveness."
How long do boosters last?
Dr Frawley says booster shots typically start to wane after about four to six months, but everybody is different.
"New variants might weigh into that as well," she said.
I'm in the 30-49 age group, should I get a fourth dose?
"I would definitely get it," Dr Frawley said.
"We've got really big case numbers.
"The vast majority of people aren't wearing masks and are only relying on vaccines for protection."
She also points out that, because the booster wanes after four to six months, you're likely to have fewer antibodies from your third dose.
Professor Nolan says it's important to remember that a fourth dose will probably have a "minimal" impact on whether or not you contract the disease.
So a fourth dose isn't all that likely to stop you from getting COVID-19, it's more about boosting your protection from getting really sick from the infection.
However, Professor Nolan also points out that people in this age group are already at a lower risk of having severe illness from the infection than people who are immunocompromised or in older age groups.
Here's more from ATAGI on that:
While rates of hospitalisation, severe disease, and death from COVID-19 are low in this age group, other factors such as time off work and the risk of long COVID may influence an individual’s personal decision to have a winter booster dose.
Why did ATAGI change its advice now?
Because there's been a surge in Omicron BA.4 and BA.5 subvariant infections.
The change aims to:
- Help to reduce severe disease from infections
- Reduce the burden on hospitals and the health system in general
Here's more from ATAGI on those new subvariants:
The Omicron BA.4 and BA.5 subvariants can partly escape the immune response generated by both prior vaccination and infection.
A first booster dose of COVID-19 vaccine has been shown to increase the immune response to these new subvariants, but wanes over several weeks.
A winter dose (the second booster dose) is anticipated to boost this immune response.
Do booster shots specifically target BA.4 and BA.5?
No.
Both Dr Frawley and Professor Nolan pointed out that, because the virus mutates so quickly, it's impossible for research to keep up the pace.
"It's an unwinnable race," Dr Frawley said.
"The good thing that we know though — regardless of variant, we know that these vaccines still provide protection, especially against severe illness."
What's the future for COVID vaccines?
It's hard to say.
"It depends on what happens in the [next] six to 12 months," Dr Frawley said.
"There'll be more vaccines — that's the one thing we know at this stage.
"The best-case scenario is these mutations slow down and we get a variant that's very mild and highly infectious and our antibody levels stay high.
"People are thinking that may happen — it's often how pandemics die out.
"But because antibodies wane so quickly, that might be unrealistic at this stage."
Professor Nolan says updated booster shots targeting more recent COVID mutations could be ready by the end of the year.
He says it's possible we might eventually end up with a multi-virus vaccine that comes out each winter — and research into mRNA vaccines should make this easier to achieve.
But he says that's for "down the track".
