Twenty crew members aboard a cargo ship docked in the West Australian port of Fremantle have tested positive to COVID-19.
The MV Ken Hou arrived on Monday, having previously visited ports in Thailand, Korea and Japan.
WA Health says two crew members who have tested negative are likely to be removed and placed into hotel quarantine.
The others will likely remain aboard the ship, with Premier Mark McGowan backing WA's experience in managing infected vessels.
"Our preference is to manage the crew on board the ship and if we can do that, that's what we'll do," he told reporters on Tuesday.
"It depends upon health advice and the condition of the crew, whether they can isolate on board and whether they're well enough to run the ship systems and the like."
Authorities are also monitoring the health of two crew members aboard the bulk carrier Poavasa Wisdom anchored near Fremantle.
About 28 per cent of West Australians have been fully vaccinated, still the lowest rate among states and territories.
The slow rollout has prompted the appointment of WA's police commissioner to a new role as the state's COVID-19 vaccine commander.
Chris Dawson will step back from day-to-day duties and assume the role effective immediately until at least the end of the year. He will remain the state's emergency coordinator, a role he has held throughout the pandemic.
WA Police Deputy Commissioner Col Blanch will take on daily commissioner duties.
Mr Dawson will be responsible for delivery of the state's vaccination program and engagement "to ensure specific hesitant groups are supported to take up the vaccine."
A record 93,000 people were jabbed last week as WA kicked off a two-week blitz and expanded eligibility to anyone over 16.
"We cannot rest on our laurels and we don't want to see momentum diminish as we get closer and closer to those important vaccine targets," Mr McGowan said.
"Dedicated leadership will help drive the program forward, putting WA in the best position to complete the rollout with innovative and fit-for-purpose strategies."
Amid sniping over the national roadmap, Prime Minister Scott Morrrison has declared Australia "has to move forward" and open up when 70 per cent of the population is fully vaccinated.
Mr McGowan has adopted a more cautious approach, stressing that the national plan includes scope for highly targeted lockdowns even at 80 per cent vaccination.
WA looms as a key battleground in the next federal election, due by May next year, with Labor likely to lean upon Mr McGowan's popularity to help their cause.
From Thursday, West Australians in NSW will be denied entry on compassionate grounds under new "extreme risk" border restrictions.
Entry will be restricted to Commonwealth, state and specialist officials, who will be forced to enter hotel quarantine for 14 days.
Hundreds of West Australians in NSW have heeded a call to return home in recent days.
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