Australia has maintained very low rates of Covid transmission throughout the pandemic due to a closed-border policy, stringent quarantine and swift testing and tracing systems.

It has recorded no deaths this year, but 910 deaths and 30,450 cases overall.

The newer, more infectious Covid variants however, have strained the nation's defences - with several small outbreaks this year.

NSW Health Minister Brad Hazzard has described the Delta variant as a "very formidable foe".

"No matter what defensive steps we're taking at the moment, the virus seems to understand how to counter-attack," he said.

Sydney's outbreak first emerged two weeks ago in Bondi, the famous beach suburb, before spreading rapidly across the city.

Its origin has been linked to an unvaccinated driver who transported international arrivals from the airport.

The NSW government has urged people to get their vaccine - noting that in one of the Sydney clusters, 24 of 30 people at a party became infected and those who didn't had been vaccinated.

"If you're vaccinated, you are much more likely to not be infected with COVID-19," Mr Hazzard told reporters on Monday.

The recent outbreaks have renewed criticism of the nation's slow vaccination rollout - which falls under the federal government's purview.

So far, just under 5% of Australia's adult population have been fully vaccinated under a phased rollout, and roughly 30% have received a first dose of either the Pfizer or AstraZeneca vaccine.

However, significant levels of hesitancy have been recorded around the AstraZeneca vaccine due to its link to a rare blood clotting syndrome. Meanwhile, Pfizer supplies have been limited to certain age groups.

Government critics have argued that cities would not need to endure lockdowns if a majority of the population was vaccinated.

BBC