Less than three weeks remain until the February 5 border transition plan, which is underpinned by projections made before the Omicron variant emerged.

Premier Mark McGowan has insisted new modelling on the impact of the highly virulent strain is still being finalised and has declined to detail any initial findings.

The government is also yet to outline planned public health restrictions or close contact definitions, including for health workers.

Residents of Perth, Peel and the South West are back to wearing face masks after a cluster of Omicron cases emerged, including two new local cases on Tuesday.

Anxiety about the expected surge in infections has coincided with several major events being called off in recent days.

Disability support group Activ on Tuesday said it had cancelled August's City to Surf fundraising run for the third straight year.

"The decision to not hold the event again this year was very difficult, however the health and safety of all Western Australians comes first so we believe this is the most responsible decision," Activ chief executive Michael Heath said.

"Our aim is to bring back this much-loved community fun run in 2023."

The City of Mandurah said it would not host its annual Crab Fest in March, citing uncertainty over potential state government restrictions.

Perth's popular Skyworks event is due to go ahead on Australia Day but attendees at the fireworks display will face spot checks for their proof of vaccination.

"If you don't have proof, you will be asked to leave the event," the City of Perth said.

Perth Festival on Monday announced it would no longer proceed with its multi-venue opening event which had been scheduled for February 11 and 12.

The festival cited difficulties with proof of vaccination requirements and the availability of staff and artists due to potential illness or isolation.

Opposition Leader Mia Davies said any Omicron modelling should be released immediately along with a community campaign devoted to detailing planned rule changes.

"Having had two years COVID-free and the luxury of time to prepare, it is ridiculous that we're three weeks out from the date set by the government and there's still confusion and haziness about how rules and restrictions will be applied, and questions as to whether our health system is ready," she said.

Multiple recent cases have been linked to U Natural Spa Therapy in the riverside suburb of Applecross, including four people who worked there.

At least one of those staff also worked at a massage parlour in Mt Lawley while infectious, prompting an urgent call for anyone with symptoms to get tested.

Rio Tinto mentioned ongoing coronavirus restrictions as it reported lower annual iron ore production in the state's Pilbara region despite record prices.

The mining giant said the restrictions had further impacted its ability to access experienced contractors and skilled workers.

Australian Associated Press