Scott Morrison says there is no magic number of vaccinations that will trigger Australia opening its international borders.

The Prime Minister is refusing to set a target date, arguing Britain still has more than 4000 daily cases despite 77 per cent of its population being vaccinated.

Australia’s chief health officials have repeatedly stressed vaccination is almost 100 per cent effective in reducing death, hospitalisations and serious illness.

Mr Morrison said immunising the population would allow the nation to consider opening up gradually.

“That will give us more and more and more options going forward, but I’m not about to swing the doors open and open Australia up to 4000 cases a day,” he told 6PR radio on Thursday.

“It’d shut the country down internally and it would ruin our economy.”

Mr Morrison said international borders would remain shut for as long as was needed to protect health and the economy.

“There’s no medical advice that I have received at any point in time which gives a magical number of vaccinations that enable you to provide that level of surety to Australians about when that can occur.”

While the federal budget assumed a gradual return to international travel from mid-2022, the federal government remains circumspect about linking vaccinations to restarting overseas travel.

Mr Morrison is due to send voters to an election between August and May.

State and territory governments have ridden a wave of popularity stemming from border closures and other tough coronavirus prevention measures.

Elections held during the pandemic in Queensland, Tasmania, the NT and ACT have returned incumbent governments.

In Britain, 77 per cent of people have received their first dose and 54 per cent both jabs.

The Australian government doesn’t release daily data about how many people have been fully vaccinated but the figure was about 3 per cent earlier in the week.

Australia’s vaccination data, as at Tuesday. Image: Federal Health Department

More than 5.3 million doses have been administered nationwide as the sluggish rollout slowly gathers momentum.

“There’s been a significant ramp up. It’s continuing to occur. Australians are getting the jab,” Mr Morrison said.

“I’m keen for wherever there’s a dose available and an arm available I want to connect those two as quickly as possible.”

Australia’s eastern states are on high coronavirus alert after a couple with the disease escaped Melbourne’s lockdown.

A 44-year-old woman and her husband have tested positive in Queensland after driving from Victoria through NSW to the Sunshine Coast.

There are now exposure sites across regional NSW and Queensland, sparking concerns Melbourne’s outbreak could spread.

Victoria had four new cases all from the same home on Thursday with authorities working to investigate the source of the infections.

Melbourne remains on track for its harsh lockdown to ease from midnight Thursday. Restrictions on travel and gatherings will remain, while masks will also be mandatory whenever leaving home.

-AAP