West Australian workers will be required to get their third dose of a COVID-19 vaccine under the state’s far-reaching jab mandate program.

About 75 per cent of the state’s workforce are subject to the mandates but they were previously only required to receive two doses.

Premier Mark McGowan says workers will now need to receive a third dose within one month of becoming eligible for the booster.

Australians are currently eligible for the booster shot five months after having their second dose of a vaccine but health authorities are looking at shortening that period.

“You need to start thinking about getting a third dose as soon as possible, before Omicron starts coming into our community,” Mr McGowan told reporters in Perth after Wednesday’s national cabinet meeting.

The premier said the plan to reopen the state’s borders from February 5 remained “locked-in barring an emergency”, with state and territory leaders set to receive advice in a fortnight’s time about the severity of the Omicron variant.

“We’ll watch what happens in NSW and other states as part of that,” he said, adding that restrictions such as mask-wearing could be scaled up at any time.

“I want us to make it to February 5.”

In the meantime, WA will further tighten its borders by upgrading Tasmania and the Northern Territory to medium risk from Boxing Day.

It means WA will have a hard border in place to all other states and territories, denying entry to any non-approved travellers.

Mr McGowan said the public health risk was very low after a man and a woman who arrived on a flight from Brisbane tested positive overnight.

The vaccinated couple, aged in their 30s, arrived on Sunday night on flight VA470, hours before WA’s reintroduced hard border to Queensland came into effect.

They are isolating along with four household contacts who have tested negative. A fifth person who briefly visited their home has also returned a negative test result.

The pair attended a testing clinic on Monday and briefly stopped by the 7-Eleven Midland service station to fill up their car. Mr McGowan said the stopover was permitted, both had been wearing masks and the woman had spent only 40 seconds inside.

Authorities have identified 104 casual contacts and 35 close contacts, 23 of whom have tested negative.

WA’s double-dose vaccination rate is nearing 83 per cent and is on track to reach 90 per cent by the time the borders reopen in February.

– AAP