As Melbourne braces for another lockdown due to another hotel quarantine outbreak, the acting Victorian premier James Merlino has warned of the high risks of the virus-spread becoming "increasingly uncontrollable".

"We've got a bigger spread of exposure sites, more than 150 exposure sites across the state," Mr Merlino said, adding that more than 10,000 primary and secondary contacts of infected people had been identified. They will have to quarantine, or test and isolate.

As he announced a seven-day statewide lockdown, Mr Merlino took aim at the federal government, saying "the vaccine rollout has been slower than we had hoped".

"If we had the vaccine, the Commonwealth's vaccine program effectively rolled out, we may well not be here today," he said.

He highlighted that the latest outbreak came from "a hotel breach in South Australia", one of many breaches in hotel quarantine "right around our country".

A world vaccine tracker [last updated on Tuesday] shows the share of people who have received at least one dose of COVID-19 vaccine in various countries.

This included: Israel (63 per cent), UK (57 per cent), US (49 per cent), Canada (53 per cent), Germany (41 per cent, Italy (36 per cent), France (35 per cent), Australia (13 per cent) and India (11 per cent).

The percentage of fully vaccinated people included: Israel (59 per cent), US (39 per cent), UK (35 per cent), Italy (18 per cent), France (15 per cent), Germany (15 per cent), Canada (4 per cent), India (3 per cent) and Australia (2 per cent).

The ABC's vaccine rollout tracker shows that we can expect to reach the 40 million doses needed to fully vaccinate Australia's adult population in early December next year, based on the current pace of about 455,000 doses a week. This is well behind the Morrison government's original and revised targets. This is nowhere near acceptable.

Only three weeks ago, University of Melbourne mathematical biologist James McCaw warned that the risk of a disastrous COVID-19 outbreak in Australia was at its highest level since the pandemic began.

Professor McCaw said it was absolutely inevitable that the virus would spread within Australia, given the spate of hotel outbreaks. The nation had, so far, been "lucky".

He said it was a matter of time before one of the outbreaks would avoid the efforts of contact tracers. Widespread vaccination of the young and old remained the only way to prevent hospitals being overwhelmed.

"The virus will win. But it won't have a devastating impact if we are vaccinated."

This warning may well come to pass with the latest Melbourne outbreak. The vaccine rollout must improve and quickly.

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