WA recorded 24 new cases on Wednesday, nine of which were linked to a lithium plant in the state's southwest.
Two infections have an unknown source, including one in the Wheatbelt.
Thousands of people were nonetheless set to flock to the banks of the Swan River on Wednesday evening for the Australia Day fireworks.
Last year's event was cancelled due to the pandemic but more than 250,000 people attended in 2020.
Premier Mark McGowan said he had been advised by the chief health officer that this year's event was safe to proceed with attendees wearing face masks.
"I expect the turnout will be down, given what's going on," Mr McGowan told reporters.
"I expect most people will do the right thing, overwhelmingly they will. You have to make these judgment calls and the advice was it was safe to do so."
The Australian Nursing Federation had called for the fireworks to be cancelled, saying it could become a super-spreader event.
Attendees were initially warned they would face spot checks for their proof of vaccination and could be asked to leave if they failed to comply.
But the City of Perth subsequently backed down, instead encouraging people to only attend if they were double-vaccinated and feeling well.
The premier noted he had attended a citizenship ceremony with hundreds of people under the same roof, albeit wearing masks.
"That's occurring all over Western Australia, these events, and often they're indoors," he said.
WA's double-dose vaccination rate has now reached 90 per cent, a threshold that was meant to trigger the reopening of borders from February 5 before Mr McGowan backtracked on the plan.
About 31 per cent of eligible West Australians have received their third dose.
Mr McGowan conceded WA had no chance of eliminating its Omicron wave as it had previous outbreaks and that the border closures would be rendered unnecessary "in due course".
But he insisted his controversial decision would buy valuable time for people to get their booster.
"If we can get that third dose rate up, we'll save scores if not hundreds of lives," he said.
Wednesday's case numbers included 13 workers at Albemarle's Kemerton lithium hydroxide plant, under construction 150 kilometres south of Perth.
Four close contacts of workers have also tested positive.
Many of those people are believed to have been infectious while in the community and the cluster is expected to grow, WA Health said.
Mr McGowan said one contractor in particular at the Kemerton site had been affected and that work area had been shut down.
Australian Manufacturing Workers Union state secretary Steve McCartney said workers feared they would contract the virus and take it home to their families.
"They are being driven to site on crowded buses from accommodation, there has been no visible increase in cleaning and no instigation of split shifts or staggered breaks," he said.
An Albemarle spokesman said all workers at Kemerton were vaccinated and the site was adhering to WA Health protocols.
Just 8368 people were tested for COVID-19 on Tuesday, which Mr McGowan conceded was not enough.
"When it gets here in large numbers, there's going to be debilitating problems," he said.
"There's going to be lots of issues. That is unavoidable."
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