The numbers used by the federal government to defend the effectiveness of hotel quarantine are wrong, one of Australia’s leading epidemiologists says.

The criticism comes amid growing calls for states and territories to have purpose-built facilities, as analysis shows purpose-built quarantine costs a fraction of the economic cost of lockdowns.

In April, Prime Minister Scott Morrison sought to downplay concerns Australia would keep yoyo-ing in and out of lockdown until issues in hotel quarantine were fixed.

“A system that is achieving 99.99 per cent effectiveness is a very strong system and is serving Australia very well,” Mr Morrison said.

“If I was to tell you [last year] that would achieve a 99.99 per cent success rate, you wouldn’t have believed me. No one in this country would have believed me. I would have found that hard to believe.”

But Mary-Louise McLaws, an infectious diseases expert at the University of NSW and member of the World Health Organisation’s COVID-19 response team, said the PM’s figure was wrong.

“I have no idea where it’s been plucked out of,” Professor McLaws told The New Daily. 

About 70 per cent of total cases since Australia closed its borders on March 20, 2020 had directly and indirectly come from quarantine breaches and exemptions, she said.

Approximately 21,000 people have been infected due to those breaches and exemption.

Professor McLaws said the Australian government needed to “turn 180 degrees and rethink” quarantine, to save itself money and protect its citizens.

“Lockdown costs $1 billion a week for NSW or Victoria,” she said.

Pointing to the Northern Territory’s Howard Springs quarantine facility, which has not leaked a single case into the community, she said states need their own purpose-built facilities, not hotels.

“Victoria has estimated they could make a purpose-built for $700 million. That’s less than the cost of a one-week lockdown,” Professor McLaws said.

“In WA, they could make a 1000-bed facility that would cost between $80 million and $200 million – that’s still a fraction.

“When people say this is too expensive, I say try $1 billion a week.”

Professor McLaws has long advocated for better practices in quarantine hotels, including enhanced ventilation, more testing and better separation of COVID-positive guests.

She has also called for rapid antigen testing on day one and 14 of quarantine stays.

“Victoria wouldn’t have had to spend that $1 billion if a traveller who inadvertently acquired COVID had been tested on the last day with a rapid antigen test, which costs $5 and takes 15 minutes,” Professor McLaws said.