The vast majority of Thursday's 754 new infections were detected in NSW, which had 681 cases of local transmission.

There were 57 cases in Melbourne and 16 in Canberra, with the combined tally of 754, eclipsing the record set last year during Victoria's deadly second wave.

While the Delta strain circulating across three states and territories is more contagious than previous variants, vaccines are another key difference in this year's fight against the pandemic.

A whopping 309,010 jabs were administered in the past 24 hours, which was another record day.

More than half of the nation's population aged 16 and above has received at least one dose, while 28.8 per cent are fully vaccinated.

Prime Minister Scott Morrison said it was a major turning point in the rollout, which has been plagued by slow progress.

"Australia is really getting on top of this on the vaccination program," he told reporters in Canberra.

"Today, a big corner turned because one in two Australians who are eligible to have the vaccine have had it."

Eligibility will be extended to everyone aged 16 to 39 from the end of the month, with about 8.6 million people in that group.

Opposition Leader Anthony Albanese said Australia had reached 50 per cent for first doses on the same day it was announced Americans would start receiving third booster jabs from next month.

"We are way behind," he told 3AW radio.

"The problem we have is that Scott Morrison said it wasn't a race and it was a race. Other countries have got ahead of us."

NSW Premier Gladys Berejiklian said every state would need to confront living with the virus when double-dose vaccination coverage reaches 80 per cent.

She expects that benchmark will be reached in about three months.

"By mid-November the conversation has to be around not so much the number of cases we have, but how many people we are keeping out of hospital," Ms Berejiklian said.

Federal, state and territory governments support vaccine coverage targets of 70 and 80 per cent to reduce the likelihood of lockdowns and reopen Australia.

While New Zealand has approved vaccinating all 12 to 15-year-olds, Australia's expert immunisation panel ATAGI is yet to make a decision.

There has been rising Delta cases among children and younger people who have been the least urgent priority of the rollout.

The prime minister says he expects a decision soon with plans being readied to expand the rollout to children.

"I am keen to see that occur this year. I think it is important it happens this year," Mr Morrison said.

Meanwhile, AstraZeneca announced the brand name Vaxzevria has been registered in Australia for its vaccine, bringing it into line with other countries.

"Use of the Vaxzevria brand name should help simplify international travel for people vaccinated with AstraZeneca's vaccine," the company said in a statement.

Melbourne marked its 200th day in lockdown with a spike in cases, however 54 were linked to existing outbreaks and 44 were isolating while infectious.

Victorian Premier Daniel Andrews said the latter figure was exactly what health authorities wanted to see.

A three-day lockdown in Darwin ended at midday after no new cases were linked to an infected US defence contractor.

However, the town of Katherine will remain in lockdown for a further 24 hours.

Australian Associated Press