Sydney pharmacist Bill Warner says the rush on booster shots started less than 24 hours after the recommendation on Sunday to reduce the time interval after the second shot.
"Since Monday - and we opened at 8 o'clock - we have been inundated with people requesting their booster shot," he said.
Those aged 18 years and over who had their second shot five months ago or longer are - a month earlier than the previous recommendation.
The change means the number of Australians eligible for a booster shot has increased from 1.7 million to 4 million.
Younger business professionals and doctors were among those in line waiting for up to an hour on a walk-in basis at the Darlinghurst practice on Friday.
"So far we have been able to meet the demand. We're doing up to 180 injections a day," he told SBS News.
But supply started to dwindle and on Friday the supply of Moderna is low and Pfizer ran out at lunchtime.
He said patients have said they were motivated by the rise in cases in Australia and overseas, and the need to plan for Christmas.
He said: "The numbers are peaking again - and what is happening overseas is quite frightening. Talking to friends overseas, the epidemic that is there.
"They want to protect themselves.
"A lot of people don't want to have a booster shot just before Christmas. If they're going to get any side effects they want to have it now, not over the festive season."
The queue at a COVID-19 testing clinic in Surry Hills, Sydney snaked around the block on 17 December 2021. Source: SBS News
Australia's Chief Medical Officer, Professor Paul Kelly, said Thursday was a "record day" for booster shots with more than 135,000 shots delivered.
Nationally, 1.1 million people have had the booster shot.
Professor Kelly said distribution issues are being worked on as he urged Australians to book an appointment.
"At the moment, there's still more than 4,500 sites across the country who have bookings available in the next one to three days.
"In terms of keeping yourself safe, your friends and family safe, the best Christmas gift is to get out and get your vaccination and boosters."
He said there was no plans to further shorten the time interval to less than five months, although there is room to get the shot one or two weeks earlier than that period.
"Because of this time of year, ATAGI is urging anyone giving vaccines to be flexible, given clinics may be closed or people may be travelling.
"But mostly, the five months is the time (ATAGI) want to stress."
The demand for PCR tests has also increased as people plan Christmas gatherings with friends and relatives.
The daily COVID-19 testing numbers has been steadily rising as Australia's most populous states register record daily COVID-19 tallies.
In NSW, the tally jumped from 104,501 reported on Wednesday, to 143,938 on Thursday and 127,583 today.
In Victoria, the reported daily COVID-19 testing figures rose from 77,066 on Wednesday, to 80,841 on Thursday and then higher still to 82,301 today.
Supplies scheduled for next week
The federal government said it was moving swiftly to adjust to an uptick in demand for booster shots after the recommended interval was reduced to five months on Sunday.
"There's no concern about the amount of supply and we'll make sure that everyone who is eligible for a booster can get that opportunity as quickly as possible," said Lieutenant General John Frewen, the head of the COVID Vaccination Taskforce.
He said a group had been appointed to monitor booster supplies and identify shortages in the days since Sunday when Australia's expert immunisation panel, ATAGI, announced the shortened time interval.
"It is being resolved as we speak," he added.
"Next week will be the largest amount of deliveries that we have done since the beginning of the program."
Experts from the OzSAGE group earlier this week urged authorities to consider further shortening the time to two months to protect the most vulnerable in the community.
On Tuesday, NSW Health Minister Brad Hazzard said he would like to see the interval reduced to as little as three months between a second dose and booster, citing the growth in Omicron cases associated with the Newcastle Argyle House nightclub.
More than 500 COVID-19 cases have now been recorded in the city.
Nationally, the double-dose vaccination coverage is 90.1 per cent in those aged 16 years and over. The single-dose vaccination coverage is 93.7 per cent.
