The COVID-19 vaccination rollout across Australia's most populous state will be delayed by heavy rains and flooding, which is cutting off access to roads.
"Vaccine delivery is being affected in Sydney and across multiple regional NSW locations," the federal health department said on Saturday.
"We ask for the public's patience and understanding with these unforeseen supply delays."
More than 250,000 virus jabs have been administered in Australia, a long way off the four million Prime Minister Scott Morrison said would be completed by the end of March.
The phase 1b rollout - for people over 70, Indigenous Australians over 55, those with a medical condition or disability, and workers deemed high risk - is due to start on Monday.
But the rollout in NSW, the nation's most populous state, is being disrupted by the heavy rain and flooding, which is blocking roads.
Sydney's Hawkesbury Nepean Valley, which includes Penrith, is set to cop its worst flooding in 60 years.
"Clearly there will be expected disruptions for many freight and logistic movements across NSW as a result of these floods. Vaccines will not be exempt from that," Finance Minister Simon Birmingham told Sky News' Sunday Agenda program.
"So we are working with our freight and distribution companies who are getting the vaccine from point A to point B to just understand about what will be impacted"
NSW Premier Gladys Berejiklian says she has yet to briefed on any delays but assumes there will be distribution challenges because of the road closures.
"I'm not concerned, we will catch that up," she told reporters in Sydney while giving an update on the flood situation.
Deputy chief medical officer Michael Kidd said distributors were doing all they could to ensure timely deliveries.
"Over 1000 scheduled deliveries have already been made and the remaining are ready to go as soon as roads are safe and practices are able to reopen and receive the deliveries," Professor Kidd told reporters in Canberra.
There were just four COVID-19 overseas acquired cases recorded in Australia on Sunday, two in NSW and two in Queensland.
Prof Kidd says this contrasts with the global situation where cases continue to be very high with more than half a million reported in the past 24 hour-period and with almost 8500 deaths recorded.
Department of Health secretary Brendan Murphy is optimistic about the outlook, as long as most of the Australian population is vaccinated.
"I think life will return to normal, but I think we have just got to be patient," Professor Murphy told Sky News.
While the vaccines are safe, he says there are still a number of things that are not known about them, such as how long the protections will last, how good they are against variant strains of COVID-19 and whether people will need booster shots every year, like a a normal flu jab.
But he does expect the vaccine rollout will allow for a reduction of all restrictions and ensure state border closures aren't needed any more.
"As we get more and more Australians vaccinated and as more and more countries around the world get vaccinated, we will start to progressively look at what sort of border and quarantine measures we have to do," the former chief medical officer said.
"We might think about, for example, reducing the length of quarantine, more home quarantine ... our risk tolerance will change over the second half of this year."
But he still believes it "does not look good" for international travel until next year.
People in Australia must stay at least 1.5 metres away from others. Check your jurisdiction's restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.
Please check the relevant guidelines for your state or territory: NSW, Victoria, Queensland, Western Australia, South Australia, Northern Territory, ACT, Tasmania.
