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Mask usage on Sydney's public transport network will be mandatory for at least five days after another local COVID-19 case popped up in a man who had "fleeting exposure" from an infected shopper.

The man in his 50s caught the virus while shopping at Myer Bondi Junction on Saturday.

He was on the same floor in the same section as a limousine driver believed to be at the centre of this week's outbreak.

NSW Chief Health Officer Kerry Chant said it appeared the limousine driver had passed on the Delta strain of the virus with just fleeting contact.

Queensland and Tasmania on Friday responded to the development by tightening border restrictions, with Queensland declaring a virus hotspot from 1am on Saturday in Sydney's Waverley council area.

Tasmania will block entry for those who attended any NSW exposure site.

"This indicates that the initial case was highly infectious as transmission must have occurred through fleeting exposure," Dr Chant told reporters.

"(This is) noting that the person who caught the infection at the cafe was seated outside and there was no known (contact) with the initial case."

As a result, mask usage is again compulsory on Sydney public transport until at least Thursday, Premier Gladys Berejiklian announced.

"Some people for some reason aren't contagious and some are extremely contagious ... the randomness of that is what makes it scary," she said.

The new case comes after an unvaccinated limousine driver from Sydney's east and his wife were diagnosed with the coronavirus and subsequently infected a woman in her 70s at a Vaucluse cafe.

The limo driver, aged in his 60s, transported international air crews.

Another case - a man in his 40s from Sydney's northwest - also tested positive for COVID-19, but NSW Health has not yet concluded if the case is genuine.

The man in his 50s will be included in numbers released on Saturday.

NSW Health on Friday evening listed a number of new COVID-19 exposure sites including the level five food court at Westfield Bondi Junction, as well as level four and the bus interchange near the centre.

It also listed Eden Gardens at Macquarie Park and the limousine car park at Sydney International Airport as new COVID-19 exposure sites.

Western Australia and South Australia previously shut the border for those who attended NSW virus exposure sites, while Victoria has tightened restrictions for residents of the City of Sydney, Waverley and Woollahra council areas.

New Zealand Prime Minister Jacinda Ardern confirmed on Friday that quarantine-free travel will continue with NSW for the time being.

© AAP 2021

The Delta variant of COVID-19, first identified in India, is becoming the globally dominant variant of the disease, the World Health Organisation's chief scientist says.

Soumya Swaminathan also voiced disappointment in the failure of CureVac's vaccine candidate in a trial to meet the WHO's efficacy standard, in particular as highly transmissible variants boost the need for new, effective shots.

The United Kingdom has reported a steep rise in infections with the Delta variant while Germany's top public health official predicted it would rapidly become the dominant variant there despite rising vaccination rates.

The Kremlin blamed a surge in COVID-19 cases on reluctance to have vaccinations and "nihilism" after record new infections in Moscow, mostly with the new Delta variant, fanned fears of a third wave.

"The Delta variant is well on its way to becoming the dominant variant globally because of its increased transmissibility," Swaminathan told a news conference.

Coronavirus variants were cited by CureVac when the German company this week reported its vaccine proved only 47 per cent effective at preventing disease, shy of the WHO's 50 per cent benchmark.

The company said it documented at least 13 variants circulating within its study population.

Given that similar mRNA vaccines from Pfizer-BioNTech and Moderna posted efficacy rates topping 90 per cent, Swaminathan said the world had been expecting more from CureVac's candidate.

"Just because it's another mRNA vaccine, we cannot presume all mRNA vaccines are the same, because each one has a slightly different technology," Swaminathan said, adding the surprise failure underscored the value of robust clinical trials to test new products.

WHO officials said Africa remains an area of concern, even though the continent accounts for only about 5 per cent of new global infections and 2 per cent of deaths.

New cases in Namibia, Sierra Leone, Liberia and Rwanda have doubled in the last week, WHO emergencies program head Mike Ryan said while vaccine access remains minuscule.

"It's a trajectory that is very, very concerning," Ryan said.

"The brutal reality is that in an era of multiple variants, with increased transmissibility, we have left vast swathes of the population, the vulnerable population of Africa, unprotected by vaccines."

© RAW 2021