Police officers patrol through the quiet Central Station in the city centre during a lockdown to curb the spread of a coronavirus disease (COVID-19) outbreak in Sydney, Australia, August 12, 2021. (Photo: Reuters)   

Australia's Prime Minister Scott Morrison on Sunday defended the country's lockdown strategy to combat coronavirus outbreaks until at least 70% of population is fully vaccinated.

On Saturday, Australian police arrested hundreds of people during anti-lockdown demonstrations in Sydney and Melbourne, capitals of the country's two most populous states, New South Wales and Victoria, that are under a strict lockdown.

The federal government announced late last month a plan that envisaged lockdowns as a key strategy to quell outbreaks until 70% percent of population gets vaccinated and a gradual re-opening of Australia's borders when that number reaches 80%. .

"You can't live with lockdowns forever and at some point you need to make that gear change and that is done at 70%," Morrison said in a television interview on the Australian Broadcasting Corp.

Victoria, in its sixth lockdown since the start of the pandemic, on Sunday recorded 65 locally acquired cases. On Saturday Australia saw its worst number of COVID-19 infections ever, with NSW and Victoria battling a growing outbreak of the highly transmissible Delta variant.

Only about 30% of people aged over 16 have been fully vaccinated so far, according to health ministry data released on Saturday.

The pace has picked up recently, as supplies increase and the Delta outbreak continues to spread. A Newspoll conducted for The Australian newspaper earlier this month suggests that 11% of Australians said they will flatly refuse to get vaccinated.

Despite a third wave of infections from the Delta variant, Australia's COVID-19 numbers are relatively low, with just over 43,000 cases and 978 deaths.

Reuters