A second worker and at least one resident have been confirmed with the coronavirus at an aged-care home in Melbourne’s west.

Confirmation of the infections came from the home’s operator, Arcare, on Monday, after local MP Bill Shorten told ABC News Breakfast he knew of at least one positive case in a resident and “possibly two”.

They were among five new COVID infections confirmed in Victoria on Monday, as the outbreak that has sent the state into lockdown grew to 45 cases.

“The resident has received one dose of the Pfizer vaccine. However, the second team member did not receive the first dose of the vaccine on May 12 as she was on personal leave when the vaccinations took place on that day,” Arcare said in a statement.

“The resident is displaying mild symptoms. However, they are being transferred to hospital where their condition can be closely monitored. The team members also have mild symptoms and are recovering at home.”

There were no new infections in hotel quarantine.

• ‘Incredibly serious’: Worried Vic authorities adds six cases to Monday’s tally as outbreak surges

Also on Monday, another aged-care home – BlueCross Western Gardens in nearby Sunshine – confirmed a female worker had tested positive for COVID.

The home told the ABC the woman was tested on Friday after a shift at Maidstone Arcare, but her results were negative.

She was tested again on Saturday and returned a positive result.

It is unclear if it is the same worker already confirmed as positive at Arcare Maidstone over the weekend, or another staff member.

Tweet from @VicGovDH

Mr Shorten said he understood both Arcare residents thought to be infected had had one shot of a coronavirus vaccine, he said.

“It just emphasises to me, and I think to everyone listening, that two vaccinations is what we need,” he said.

The latest cases follow confirmation of a mystery infection in one of the home’s staff on Sunday. The woman, who lives in the western Melbourne suburb of Altona, was one of five local cases reported on Sunday.

She tested positive despite receiving her first dose of the coronavirus vaccine on May 12 and is thought to have been infectious last Wednesday and Thursday.

Also on Monday, two more nearby aged-care centres – the Royal Freemasons Footscray and Coppin Centre – were sent into lockdown.

Australian Nursing and Midwifery Federation Victorian branch secretary Lisa Fitzpatrick told ABC radio Melbourne she understood the Arcare Maidstone worker did shifts at both those locations.

The Maidstone facility was locked down and residents were placed into self-isolation on Sunday the woman’s positive test.

Only a third of Arcare Maidstone’s 110 staff and 53 of 76 residents have so far had even single vaccine shots. The federal government has brought forward scheduled second doses to Monday.

“We are encouraging all the residents and families of those who have not provided consent to reconsider,” federal Health Minister Greg Hunt said.

He said 85 per cent of residents in private aged-care facilities and 100 per cent in Victorian residential facilities had been vaccinated.

The latest came as leading epidemiologist and member of the World Health Organisation’s health emergencies program expert advisory panel Professor Mary-Louise McLaws told Melbourne radio 3AW the aged-care “mystery case” was “the most concerning part” of Victoria’s latest virus outbreak.

She said the state’s seven-day lockdown – scheduled to end at midnight on Thursday – should be extended for another week.

With the addition of Monday’s cases, Victoria’s outbreak has reached 45 infections.

“We always expect, in small clusters, to have at least 14 days or twice an average incubation period of zeros to ensure you’ve flushed out every possible case,” Professor McLaws said.

“I would have wanted another week.”

“Sadly, I would expect at least another case or two because these residential carers have multiple people they care for … and you can’t keep your distance when you’re caring for people,” she said.

Ms Fitzpatrick said vaccination rates at the Maidstone home demonstrated Canberra’s “go-slow culture” on aged care.

“The hindsight of almost 2000 Victorian aged-care residents contracting COVID-19, 655 resident deaths and more than 1600 aged care workers infected was not enough to motivate the Morrison government into urgent action,” she said.

The Arcare home was one of 40 locations added to the state’s list of exposure sites on Sunday. Others include a soft drink factory in Thomastown, bus routes in Melbourne’s north and west and shops at Chadstone shopping centre.

• See an updated list of Victorian exposure sites here

Craigieburn’s Willmott Park Primary School was closed on Monday, with nearby Mount Ridley College listed as an exposure site after a pupil tested positive for COVID-19 on Saturday.

Acting Premier James Merlino said no decision had been made on whether the Victorian lockdown would end on Thursday night as planned.

“This is something that is evaluated every hour of every day,” he said on Sunday.

State Treasurer Tim Pallas accused the federal government of failing to aid stood-down Victorian workers, as he announced a $250 million business support package.

-with AAP