With less than six weeks to go until Western Australia's border opens to the rest of the country and the world, eligible residents were already being urged to get COVID booster shots.
Earlier this week, the state became the first to put an expanded mandate in place, requiring workers already covered by vaccine rules — around 75 per cent of the WA workforce — to receive a third dose of a vaccine.
When announcing the move, Premier Mark McGowan said vaccination was the state's best defence ahead of the planned border easing on February 5.
"Everyone is strongly urged to receive their third dose when eligible, even if not covered by this [mandate] policy," he said.
Now, with a positive case visiting multiple locations across Perth, hundreds of casual contacts sent to get tested, and masks in place for the festive period, that push is even stronger.
UPDATES: Read our round-up of the latest news on the COVID-19 pandemicWhen am I eligible for a booster?
Changes to the booster time frame were announced on Friday.
Currently, boosters are recommended for anyone over 18 who received their second dose of a COVID vaccine five months ago.
This will change in coming weeks, after advice from the Australian Technical Advisory group on Immunisation (ATAGI).
From January 4, the time frame will be four months after your second dose, and from January 31, three months.
Many states had been pushing for a shorter time frame.
Professor Jaya Dantas from Curtin University's School of Population Health said a shorter time frame made sense with the growth in the Omicron variant.
Epidemiologist Jaya Dantas agrees with shorteing the timeframe to get the booster shot.(ABC News: Keane Bourke)
"With the Omicron variant already in Australia and over the world, I think reducing that timing from five months to between three and four months will be much more effective at this stage," she said.
What difference does a booster make?
AstraZeneca does not appear to provide good protection from Omicron infection but does offer protection from severe illness.
With the Omicron variant spreading fast around the world and set to become the dominant COVID-19 strain in the UK, there is one question everyone wants to know.
mRNA vaccines like Pfizer and Moderna are also less effective at stopping Omicron infections, although early data suggests a booster helps restore this protection.
Essentially, two doses of a vaccine will help protect against severe disease and death, but a booster will help prevent infection.
A booster shot pushes your antibody levels back up to around where they were just after you were fully vaccinated.
Pfizer and Moderna are both recommended for use as a booster vaccine, while AstraZeneca can be used for people with contraindications to those vaccines.
If you are not eligible for a booster before the border opens but have had two doses of a COVID vaccine, Chief Medical Officer Paul Kelly has reassured people protection does not suddenly disappear.
Vaccination rates in Western Australia remain lower than other states.(ABC News: Rebecca Trigger)
"Just because you get to three months, four months, five months or six months, you do not immediately lose your protection, that's not the case," he said.
But, he said a booster will push your Omicron protection back up towards the same level you had against the Delta variant.
How does the vaccine mandate expansion affect me?
All WA employees already mandated to be vaccinated for work purposes will be required to get a booster.
Those rules cover around a million people.
Group 1 industries — those deemed to have high transmission risk, like police, care services and border control — need to have two doses by December 31.
Group 2 industries — those deemed critical to the ongoing delivery of key services to the community like supermarkets, public transport and child care providers — need to have two doses by January 31.
The state government said after that second dose, people in the mandated industries need to receive their booster within a month of becoming eligible.
Mark McGowan has made the booster shot mandatory like first and second doses.(AP: Tatan Syuflana)
Due to the changing booster time frames, when that needs to happen will vary, but if someone in Group 1 got their second vaccination on the December 31 deadline, they would need a booster between the end of March and the end of April, as the three-month recommendation will be in place.
Likewise, if someone in Group 2 got their second vaccination on the January 31 deadline, they would have to get a booster between the end of April and the end of May.
Where can I get a booster?
There are lots of places to get a booster shot around WA, including state-run clinics like Claremont Showgrounds, GPs and pharmacies.
How do you find out when you're eligible?
WA Health says a combination of email and SMS notifications are used for those who received their first or second vaccination at a state-run clinic.
But not everyone has received those, so it's worth keeping an eye on the time passed since your second vaccine dose yourself.
Transport Minister Rita Saffioti said, "they are working on the reminder situation".
"It's also good to check your vaccine certificate and you can ring up and get advice about booking a booster shot," she said.
How many people have had their booster?
Police Commissioner and Vaccine Commander Chris Dawson said that as of December 23 around 100,000 people had had a third dose of a COVID vaccine.
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Professor Dantas said it would take a significant effort to get people boosted before the border opened.
"We knew that between now and February 5, we needed 200,000 West Australians to get their second dose," she said.
"Those who have actually taken both the doses, to get them to have the booster dose would be a big effort."
As of December 23, 83.2 per cent of the WA population aged 12 and over had received two doses of a vaccine.
Vaccination rates in Western Australia remain lower than most states and territories.
How many boosters can be given before the border opens?
WA Health says as of December 24, with new booster time frames in place, around 950,721 people will be eligible between then and February 5 to receive a third COVID vaccine dose.
Some of those third doses will be as part of an immunocompromised person's regular schedule — they get three doses as standard.
Will children be vaccinated in time?
The Pfizer vaccine will start being offered to kids between five and 11 from January 10 — that dose will be one-third of the dose given to people 12 and over.
The WA Government said that date is in line with the expected vaccine supply from the federal government.
The recommendation for this group is that two doses are given, eight weeks apart, so there will not be time for a second dose before the border opens.
That interval is based on data from Canada, and it can be shortened to three in special circumstances like a significant outbreak.
Professor Dantas suggested one shot would be sufficient until young children could get a second.
"One shot in those kids would be enough — we've had other populations in other parts of the world who've been vaccinated with Pfizer for five- to 11-year-olds," she said.
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