With the COVID-19 Omicron strain spreading rapidly amid large Christmas gatherings, the state's top doctor is urging people to book in for a booster shot as soon as possible.
Chief Health Officer Kerry Chant says anyone who received a second dose of a COVID-19 vaccine five months ago should now "get vaccinated before Christmas".
Anyone who is immunocompromised may need a booster as part of their primary course and should consult their GP, she said on Monday.
The Kirby Institute's epidemiologist Raina MacIntyre agrees, saying adults need to start thinking about three shots of a COVID-19 vaccination as being the number required to be fully vaccinated.
"Thinking you're fine with two doses, if Omicron is going to spread in Australia, is a false sense of security," she told ABC radio.
Early data indicated that even after three doses antibody levels "start to wane pretty quickly as well".
"So it may well be that we need another fourth dose within less than a year," she said.
The double-dose vaccination rate of those 16 and older remains at 93.1 per cent, falling just short of the 95 per cent milestone on Dr Chant's wishlist.
From Wednesday unvaccinated people will be free to mingle with everyone at pubs, cafes, gyms and shops as a swathe of restrictions are lifted.
Meanwhile, NSW Health is battling to contain several large transmission events, while there are now 64 cases of the new strain now on record.
"There were nine new cases confirmed with the Omicron variant overnight, and more are expected as results of genomic testing are confirmed," NSW Health said.
The cases linked to an outbreak at Newcastle's Argyle House nightclub spiked from 24 to 84 overnight and "a number of these cases are likely to be the Omicron variant".
The outbreak started after four people who partied at the club on Wednesday had COVID-19, with the cases linked to the outbreak spawned on a Sydney Harbour Cruise of 140 people on December 3.
All 680 people who checked into the Newcastle nightclub with a QR code between 9pm on Wednesday and 3am on Thursday are close contacts and must immediately get tested and isolate for seven days.
Dr Chant said it's "incredibly important" that anyone at the venue get a test - as well as their household contacts "given the high transmission at this venue".
NSW Health is also urging anyone who was at Newcastle's Finnegan's Hotel in Darby Street on Friday night to get tested and isolate for seven days as they are considered close contacts of confirmed COVID-19 cases who were there.
"All household contacts of close contacts must also be tested and self-isolate until a negative result is received by everyone in the household," it said in a statement.
"It is likely some of these cases have the Omicron variant of concern."
Dr Chant is also urging people to consider doing a precautionary rapid antigen test at home before socialising.
However, anyone with symptoms must do the more sensitive test available at a COVID clinic.
There were 536 new cases of COVID-19 in NSW in the 24-hours to 8pm on Sunday, as fully vaccinated people started returning to Queensland.
There were emotional reunions at Queensland airports as people welcomed loved ones after the requirement to quarantine ended on Monday.
Some 74,997 COVID tests were recorded on Sunday and there were no further deaths.
There are 171 people are in NSW hospitals with the virus, 24 of them in intensive care.
Some 81.4 per cent of teens aged 12-15 have had one dose of a COVID-19 vaccine, while 77.7 per cent are fully jabbed.
Australian Associated Press
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