Greg Hunt has ordered Australia's vaccine experts to review the timeframe for Covid-19 booster shots in light of the African Omicron variant.
Boosters are currently handed out six months after the second dose but the gap could be shortened to maximise protection against the new mutant strain which is believed to be at least as contagious as the Delta strain.
Speaking to reporters on Monday morning, the Health Minister said: 'I have asked ATAGI to review the booster time frames in light of international evidence more generally with regards to immunity and also in light of the Omicron variant.
'And we will, as ever, allow them to act independently and continue to follow their advice. But we're prepared with supplies.'
Greg Hunt has ordered Australia's vaccine experts to review the timeframe for booster shots in light of the Omicron variant. Pictured: Prime Minister Scott Morrison gets his booster shot in Sydney on November 19
Mr Hunt was asked if the timeframe would be reduced to four months after the second dose but said: 'I wouldn't speculate on any timeframes.'
The Omicron variant was identified in South Africa on November 11 and has since spread to countries around the world including the UK, the US and Australia.
Amid fears it could make vaccines less effective, Australia shut its borders to nine nations in southern Africa on Saturday but at least two cases have been identified in Sydney with a possible third being investigated.
The third suspected case was in a traveller among the 141 who recently flew into Sydney from one of the nine most affected southern African countries.
'There are two, possibly three, positive cases among those 141,' the premier said on Monday. 'Travellers on five flights over the last 24 hours are in our health quarantine facility.'
But one of Australia's top doctors and the PM have insisted there is no reason for panic yet over the new strain, which is thought to be even more infectious than Delta.
Initial studies have found that although Omicron spreads faster and is more contagious, its effect may be milder on vaccinated patients.
The new suspected case was among the 141 who recently flew into Sydney from one of the nine affected southern African countries (pictured, passengers arriving at Sydney Airport on Monday morning)
Chief Medical Officer Paul Kelly said it would be his 'Christmas present' for a more contagious but less severe variant to rip through Australia because it would boost people's immunity without causing harm.
In Monday's press conference he was asked: 'What's your view of the idea that a mild version of Covid that spreads rapidly could contribute to immunity, top-up people's ability to stave off maybe more severe versions of the virus?'
Professor Kelly replied: 'I think this morning in my media interviews I said that would be my number one Christmas present. And it would be, if that was how it ended up.
'That would be certainly a very interesting change and a positive one. But I just really say very clearly we're not in that position yet to make that statement, that that's definitely how it's gonna end up. But hope for the best and plan for other things.'
Prime Minister Scott Morrison said there was no evidence the current vaccines were not effective against Omicron as he prepared for an emergency meeting of national cabinet.
'Of course it is concerning, and that is why we’re getting all the information we possibly can,' Mr Morrison said.
'We are not in the situation we were in back in the first half of 2020. We have 86.7 per cent of the population vaccinated.
'We have already had 13 other strains which have presented. This isn't the first of the new strains we have seen, and the evidence to date does not suggest it is a more severe form of the virus.
'On issues of transmissibility and impact on vaccine, there is no evidence yet to suggest there are issues there.'
Prime minister Scott Morrison (pictured) said there was no evidence the current vaccines were not effective against the new Omicron variant and Australia was in a far stronger position with almost 87 per cent of the population vaccinated
Authorities believe a third case of the Omicron Covid variant is in Sydney, NSW Premier Dominic Perrottet (pictured) warned
On the agenda for the national cabinet meeting will be the imminent re-opening of Australian border to international student - with gates set to open on Wednesday, December 1.
NSW Premier Dominic Perrottet said he wouldn't be bringing back hotel quarantine for new arrivals just yet as 'we need to learn to live alongside the variants.
'Ultimately we need to open up to the world. We need to do so safely, we don’t need to have a knee-jerk reaction, we need to have a proportionate and balanced response.'
However, anyone arriving from South Africa, Lesotho, Botswana, Zimbabwe, Mozambique, Namibia, Eswatini and Malawi now needs to isolate at a health facility for 14 days under the new emergency measures.
Anyone arriving from South Africa, Lesotho, Botswana, Zimbabwe, Mozambique, Namibia, Eswatini and Malawi will now need to isolate at a health facility for 14 days under the new emergency measures (pictured, ADF personnel greet travellers in Melbourne in 2020)
Anyone arriving in NSW from anywhere else in the world will need to isolate at home or their accommodation and await further health advice.
At this stage, Mr Perrottet said there were no plans to bring back hotel quarantine in NSW and he stressed the importance of the state's high vaccination rate in protecting the community.
'We're very confident based on our higher vaccination rates,' he said. 'That is not the case in these southern African nations.
'Vaccination is key to NSW being able to continue to open up safely. Our number one priority is to keep our people safe, keep businesses open and keep people in work.'
Anyone arriving from South Africa, Lesotho, Botswana, Zimbabwe, Mozambique, Namibia, Eswatini and Malawi will now need to isolate at a health facility for 14 days under the new emergency measures (pictured, swab testing in Sydney Airport)
But Christmas holiday plans could be thrown into chaos as international and state border closures begin to domino and panic spreads about the emergence of the 'super-mutant' Covid variant Omicron.
Queensland reported five new cases on Monday from one family who had recently arrived after travelling through Pakistan. They are together in hotel quarantine 'as a family unit' while testing goes on to identify the strain they are infected with.
But deputy premier Steven Miles said the state would be taking a cautious approach before implementing any new restrictions.
'As they always do, the health officials are monitoring issues around the world and if that should affect things here,' he said. 'Nothing has changed at this moment.'
South Australia and Western Australia tightened border restrictions as other premiers around the nation also start to consider harsher controls.
Scientists are in a race against time to answer three vital questions about the variant that doctors said caused 'unusual' symptoms.
The Australian Health Protection Principal Committee, which gave the prime minister an emergency briefing on Sunday night, are scrambling to determine how transmissible Omicron is, whether it is more severe than other strains, and if it is vaccine resistant.
Christmas holiday plans are being thrown into chaos as fears of international and state border closures domino following the emergence of the super-mutant Covid variant Omicron. Pictured: Passenger arrive at Sydney Airport
However one of Australia's top doctors says the country may actually want the new Omicron variant of Covid-19 to spread as he warns the nation not to panic.
Dr Nick Coatsworth said early reports from southern Africa suggested the new strain may spread communities faster, but the symptoms were far milder in vaccinated patients.
'If this is milder than Delta you actually want it to spread within your community,' the former deputy chief medical officer told Nine's Today show on Monday.
'You want it to out compete Delta and become the predominant circulating virus. So, that shows you how much more we have learn about this
'It could be that we want Omicron to spread around the world as quickly as possible.'
Australia slammed its international borders shut to nine African nations where the strain first appeared earlier this month.
Trade and Tourism Minister Dan Tehan said he couldn't rule out restrictions to other nations if the outbreak spreads, or more drastic measures if Omicron turned out to be dangerous.
'We've taken a cautionary approach, that's what we'll continue to take as we work through what this variant is all about and what potential impacts it may have,' he said.
'We think that's got the balance right at the moment, but there's obviously more work that needs to be done in understanding the new variant and the potential impacts it might have.'
Mr Morrison said after his meeting: 'We need to be very responsive to the further evidence that is becoming available and the expert medical advice.
'The goal is to ensure that our public hospitals and health systems are able to cope with this virus so we can live with the virus.'
Passengers undergo COVID-19 tests at the Histopath Diagnostic Specialists pre-departure area at Sydney International Airport on November 28, 2021 in Sydney, Australia
Passengers wear face masks as they arrive at the departures terminal at Sydney Domestic Airport in Sydney
The three things scientists must know about Omicron
1. How transmissible the new variant is compared to other Covid strains?
2. Will Omicron cause more severe illness than other than variants like Delta?
3. Is the super-mutant strain resistant to vaccines?
NSW, Victoria, and the ACT temporarily re-imposed a 72-hour self-isolation requirement for all international arrivals.
Two other passengers who tested positive to Covid after arriving from southern Africa, one in Sydney and another at the Howard Springs facility near Darwin, are being screened to see if they also have the Omicron variant.
Victorian health authorities are also investigating whether the potential third NSW Omicron case could have infected anyone there while on a trip to Victoria.
Government sources said the Victorian Government was considering extending quarantine and reintroducing mask mandates in some settings.
New health orders could be announced as early as Monday, the sources said, and were likely to be also rolled out by state and territory leaders across the country.
NSW Jobs Minister Stuart Ayres announced on Sunday the state government was prepared to clamp down on travellers arriving from overseas.
'We will take the necessary measures, including restarting quarantine if required, to protect our community and our economy,' he said.
A government source said work was underway to restore hotel quarantine if required, but the preferred option will be home isolation unless the strain was deemed extremely severe.
WA Premier Mark McGowan on Saturday evening shut his state's borders to South Australia in a draconian effort to lock out the mutant new strain, as it allows in visitors from NSW and Victoria.
The ruling means only vaccinated South Australians can enter WA, where they must immediately go into quarantine for 14 days.
South Australia also tightened its border rules following the emergence of the Omicron variant.
All international travellers and people arriving in SA from high-risk locations in Australia will once again be required to quarantine for 14 days.
Pictured: Dr. Angelique Coetzee, the South African doctor who first alerted authorities to the presence of the COVID-19 omicron variant reported that it presents "unusual but mild" symptoms
First discovered in South Africa, Namibia, Zimbabwe, Botswana, Lesotho, Eswatini, the Seychelles, Malawi and Mozambique, the variant has since spread to several other nations across the globe.
The doctor who first raised the alarm on Omicron said patients are presenting with 'unusual' symptoms.
Dr Angelique Coetzee, who runs a private practice in the South African capital of Pretoria, said she first noticed earlier this month that Covid patients were presenting with odd symptoms.
The doctor, who has practiced for over 30 years and chairs the South African Medical Association, said none of the Omicron patients suffered a loss of taste of smell typically associated with Covid.
Instead they presented with unusual markers like intense fatigue and a rapid pulse.
'Their symptoms were so different and so mild from those I had treated before,' Dr Coetzee told The Telegraph.
She was compelled to inform South Africa's vaccine advisory board on November 18 when she treated a family of four, all of whom were suffering with intense fatigue after testing positive for Covid-19.
Australian virus expert Professor Tony Blakely it will take weeks before more is known about the strain and if it's resistant to vaccines.
'It's quite likely that this will precipitate new branches of vaccine development, there's just so many mutations on this virus it would seem most likely we will need new vaccines,' he told the Herald Sun.
That bleak possibility could send much of the globe back into lockdown but he said there could be one upside.
If Omicron is more infectious but less deadly and results in less hospitalisations, it could displace Delta as the most common form of Covid but lower the global death toll.
On the other hand: 'the worst-case scenario is it's more infectious, it's more virulent, and it's resistant to current vaccines,' Professor Blakely said.
US and Europe earlier placed six countries on the red list before Australia added another three - Malawi, Mozambique and Seychelles
The manufacturers of the Pfizer vaccine, BioNTech, said even if the new variant is resistant to vaccines it could create and ship a modified jab within 100 days.
Australian Industry Group chief executive Innes Willox worried an overreaction to the new variant could be almost as bad as the virus for businesses that were already struggling in the wake of Delta lockdowns.
'While some caution is understandable, the response to any new and inevitable variant needs to be targeted, proportionate and take into account the nearly 90 per cent of us are vaccinated and tired of lockdowns and border closures,' she told The Australian.
'We are just getting our economy back on its feet, but investment and confidence are still uncertain. An over-reaction both in terms of timing and proportionality around shutting Australia off from the world, and state from state, would be devastating.'
Australian Chamber of Commerce and Industry chief executive Andrew McKellar also warned that 'with international and domestic border closures finally reopening, business cannot afford to take a backwards step'.
'State and federal leaders must stick to the national plan to get Australia back open, and to stay open,' he said.
'Continuing to drive up the vaccination rate and encouraging everyone to get a booster shot is the best way to protect the population, rather than imposing further restrictions.'
Flight Centre founder Graham Turner is resigned to the fact the travel sector will see a huge decline in bookings over coming days and weeks.
'If the vaccines are effective against the new strain, it won't change anything in the medium term,' he said.
'It just depends on how panicked governments get, it's a political thing, they have to show they're doing something.'
University of NSW epidemiology professor Mary-Louise McLaws said 72-hour self-isolation in NSW and Victoria was not enough and advocated a return to 'Fortress Australia' immediately.
'Omicron still not fully understood. Is transmission faster, does it reduce vaccine efficacy, is it as hard to mitigate outbreaks [like] Delta?' she tweeted on Sunday.
'Until +90% vaccination coverage of total pop (not just +12yr) quarantine must be supervised for every traveller from every country. [With] testing on day-1, 4, 5.'
Dr Paul Griffin, director of infectious diseases at Mater Health in Brisbane, was far less concerned and said it was still too early to judge the risks of Omicron.
'I don't think we're back to square one. A lot of us thought this is what this virus is going to keep doing, going to keep evolving and we are going to keep finding new variants,' he told ABC.
Similar sentiments were echoed by Victorian chief health officer Brett Sutton, who conceded that it was 'impossible' to keep the strain off Australian shores but measures were already in place to reduce its spread.
Professor Sutton said he was 'very confident' vaccines would provide some level of 'cross protection' for the new variant, even if Omicron differs significantly in terms of 'how our immune system recognises it'.
'This is not back to the beginning,' he said.
'We are not back at square one by any means. The vaccination coverage that we've got - over 90 per cent of eligible Victorians being fully vaccinated already - is absolutely more than useful.
'It is absolutely critical in protecting them and will, I'm sure, provide protection against these variants as well. We just need to understand how much.'
University of NSW epidemiology professor Mary-Louise McLaws has called for all international arrivals to be subjected to strict quarantine rules. Pictured: A nurse prepares a Covid test at the pre-departure area at Sydney airport on November 28
Professor Sutton said 'not really enough' is known about Omicron but it seemed likely it would become the new dominant variant of Covid.
'It certainly seems to have spread very quickly in southern Africa, and in the republic of South Africa in particular across many, many provinces and numbers have increased very significantly over a short period of time,' he said.
'We just need the time to be clear about whether this virus is in this country already, and the extent to which it has spread globally.
'It's going to be impossible to keep out, I imagine. If it's more transmissible than Delta, then it will become the global variant for sure.'
Despite Professor Sutton's assurance, fatigued Victorians who are fresh out of Covid lockdown are already bracing for reinstated restrictions that may be cast over the state to tackle the new variant.
Rhonda Andrews, chief executive of the corporate and private psychology service the Barrington Centre, said the company's 320 psychologists were being bombarded with calls as anxiety heightens over the unfolding situation despite general optimism around reopening.
'We're going to get people who are going to feel like that optimism has just been shattered and they feel like, 'Here we go again',' she told The Age.
Ms Andrews said the latest health threat was likely to cause a state called 'cumulative distress'.
'What happens when people get into that mood or mindset is that they go back to what they've experienced since March 2020. It's not just as if they are dealing with the new variant, they actually relive what they've lived in the past 20 months,' she said.
Mr Perrotet said the strain could be contained and the state's timeline of lifting restrictions at 95 per cent vaccination or on December 15 was on track
The two infected passengers were on Qatar Airways QR908, via Doha, which touched down around 7pm. Twelve other passengers on the same flight who travelled from southern Africa are undertaking 14 days of hotel quarantine.
As well as the two arrivals in Sydney, another two African arrivals have also tested positive for Covid in different states and the same testing will be done on their samples to identify the strains.
The first arrived in NSW on November 23 before travelling to Victoria two days later, sparking fears Omicron is already in the southern state.
Victorian health officials will complete a full interview with this case tonight to track down any close contacts in the event the passenger does have the Omicron variant.
The second, a man, arrived on a repatriation flight from South Africa to the Northern Territory on Thursday and was in isolation at the Howard Springs quarantine facility.
Meanwhile, Queensland authorities said they were unable to guarantee the state's border would reopen once 80 per cent of the state's population was vaccinated as planned, in light of the emerging health threat.
Acting chief health officer Peter Aitken said officials were monitoring the situation and incoming visitors from hotspots interstate may be subjected to quarantine.
'We'll make that decision when there's evidence available that needs a change in position. But at this stage there's no evidence available to support a change in position,' he said.
There are 10 people from the nine southern African countries of concern quarantining in Queensland.
Victorian Chief Health Officer Brett Sutton said he was 'very confident' current vaccines would provide some level of 'cross protection' for the new variant
If it is more transmissible than Delta, as feared, experts said Omicron could become the second-most contagious disease after measles.
'What we always feared is a mutant that comes up that can spread faster than delta and can have the features of beta which is more immune evasive,' Sydney University virologist Tony Cunningham told AFR.
Omicron, deemed a 'variant of concern' by the World Health Organisation, has more than 30 mutations in the spike protein alone, and Professor Cunningham said the changes were surprising.
'It really gives the lie to the early thoughts that we had that this is not a particularly mutating virus. If it's more spreadable than Delta, it's approaching the second-most spreadable virus that we have, which is chicken pox. Number one is measles. Delta was number three,' he said.
'But if Omicron beats delta then this is a real issue for the world.'
Professor Cunningham said he believed the vaccines would still remain partially effective against Omicron but the duration of immunity could be shortened, with studies underway to determine how the strain interacts with those antibodies.
The prime minister urged people to get vaccinated as it was by far the best way for Australia to defend against any form of Covid.
'I want to encourage it and if you've already had your vaccine, your second dose and it is six months, please go and get your booster shots,' he said.
'Booster shots are very important to ensure Australia is in as strong a position as we can to deal with these sorts of issues. This is not like it was back in February and March and 2020.'
Mr Morrison said the government had good advice on Covid.
'The uncertainties are not like they used to be. We have good systems which have been proven which is demonstrated by one of the lowest fatality rates, strongest economies and highest vaccination rate in the world,' he said.
He said the Australian people and the government has worked 'to open safely and remain safely open'.
NSW recorded 185 new Covid-19 on Sunday morning, while Victoria recorded 1,061 new cases and four deaths.
Health Minister Greg Hunt said the government would not hesitate if more needed to be done to combat the Omicron strain.
'Overnight international evidence came in and we took the immediate steps yesterday and will continue to do that to protect Australians,' he said.
'Yesterday, there were over 3,800 passengers who arrived in Australia... 54 were from southern Africa.
'They had been there and identified in the previous 14 days across the nine countries and what we are pleased to see is that all of the orders that were issued yesterday had been put in place, actions had been taken, Border Force is implementing in states and territories and public health is supporting.'
Northern Territory authorities as yet have no genomic sequencing in relation to the passenger's infection strain, NT Health Minister Natasha Fyles said.
But the person has been in supervised quarantine at the national Howard Springs facility, south of Darwin, since arriving, she said.
'So there is a very low risk to the community and we wish that person well,' Ms Fyles said.
NT health chief Dr Charles Pain says he expects the sequencing test results for the South African case to be processed by Monday.
The passenger arrived in Darwin on Thursday and his positive virus result was confirmed on Friday evening.
Passengers undergo COVID-19 tests at the Histopath Diagnostic Specialists pre-departure area at Sydney International Airport on November 28, 2021
The new quarantine restrictions came into effect at midnight on Saturday and require all international arrivals in the three states - including fully vaccinated passengers - to be tested when they land.
The nine African nations from which entries to Australia have been banned are: South Africa, Lesotho, Botswana, Zimbabwe, Mozambique, Namibia, Eswatini (formerly Swaziland), Seychelles and Malawi.
Dr Griffin, from the Mater Health in Brisbane, said 'The way we've controlled this virus so well so far will still work, will still help us.
'Things like masks, social distancing, ventilation will protect us from Omicron.
'The main thing is we still don't really know the properties of this variant, so it certainly has a large number of concerning mutations but now we have to establish what that means in terms of how infectious it is...
'Its capability to evade our vaccines, and all of that hasn't been established yet, so he we just need to get that information now,' he said.
The introduction of self-isolation rules in the three states comes only four weeks after Victoria and NSW removed hotel quarantine requirements for fully-vaccinated travellers on November 1.
The ACT ended hotel quarantine for overseas arrivals on November 12.
The Victorian health department says the new rules will apply to unvaccinated children under 12 and unaccompanied minors, along with any household contacts of the returned travellers.
All airline cabin crew arriving from overseas into NSW will also have to isolate for 14 days or until their next departure.
These rules are slightly different in Victoria with vaccinated cabin crew to isolate for 14 days if they had been to one of the nine African countries of concern.
Passengers disembark off a Qantas flight after landing at Sydney Airport. Three arrivals to Australia on flights from Africa have tested positive for Covid, prompting urgent analysis of their samples amid fears they could be carrying the Omicron strain.
Chief medical officer Paul Kelly said authorities were also in the process of tracking down about 100 Australians who recently arrived from the blacklisted countries and will now need to go into quarantine for two weeks.
Professor Kelly warned it was too early to tell if Australia would be plunged back into lockdown if the virus made its way across the Indian Ocean.
'In terms of ruling in or out, what else we might do, as the health minister has clearly said, we will do what we need to do,' he said on Saturday.
'At this stage, to move toward speculation about where we might end up in Australia, even if it came here, and we don't have it here yet, that is premature.'
He said while little was known about Omicron, it was 'quite different' to previous variants of concern.
'We do not, at this point, have any clear indication that it is more severe, or any definite indication of issues in relation to the vaccine.'
Mr Kelly added that there was too little information about the current variant to make any long-term decisions.