Australia has fallen 3.4 million doses short of its target of delivering four million Covid vaccinations by 31 March, prompting criticism of the government.
The 85% shortfall comes two days after Brisbane entered another snap lockdown to combat a small outbreak.
Last week the government said the vaccine rollout did not demand urgency given Australia's low infection rates.
The country has recorded 909 deaths and 29,300 cases since the pandemic began - far fewer than many other nations.
But sporadic outbreaks have led to six lockdowns in cities in recent months. Critics say situations like Brisbane's outbreak show why a quick vaccine programme is still needed.
Brisbane's two clusters have been linked to a nurse and a doctor who contracted the virus from a Covid ward at the same hospital.
It's unclear why those health workers had not yet been vaccinated, officials said.
Critics have accused the government of mishandling the rollout, which began on 22 February - later than in many countries.
Australia is administering the Pfizer and AstraZeneca vaccines and has a rate of 2.3 vaccines per 100 people. That is expected to increase in coming months as vaccine access is opened up to the wider population.
On Wednesday, Health Minister Greg Hunt said a record 72,826 vaccinations had been given in the past day - taking the total to 670,000.
"That's showing that the national vaccination programme is accelerating exactly as intended in the manner that was intended," he told reporters.
But in January, Prime Minister Scott Morrison promised to have four million people inoculated with their first shot by March.
Earlier this month, the government pushed that target back to April, and said six million people would be vaccinated by mid-May.
It has also dialled back a promise to have every Australian fully vaccinated by October - now saying that everyone will have received a first shot by then.
Australia is currently up to stage two of its four-phase rollout for its 25 million population.
Doses are being offered to people over 70, those in aged care homes, frontline health workers, emergency services workers, Aboriginal and Torres Strait Islander people over 55, and people with underlying health conditions.
Authorities have not specified why the pace has been so slow, but issues such as booking technicalities have been reported. There are also reports that some people are choosing to not get the vaccine.
Natural disasters - such as the massive floods in eastern Australia last week - have also disrupted the rollout.
Earlier this month, the EU blocked a shipment of AstraZeneca doses to Australia, arguing there was a greater need for them in Europe.
Australia said the one shipment of 250,000 doses would not greatly affect its own programme, as it built up its own manufacturing capability.
However, Australia has asked the EU to review the ban on its order, which Mr Morrison said had been paid for.
Labor opposition leader Anthony Albanese said the government, by its own admission, could not blame international supply issues.
"They said that target wasn't dependant on anything else and they would certainly reach the target," he told the ABC.
"Yet again it's an example of how Scott Morrison is always strong on announcement and weak on delivery."
Concerns in Brisbane
Queensland's capital reported two more community transmission cases on Wednesday, bringing the outbreak to 15 infections in total.
There are fears that the city's three-day lockdown, due to finish on Thursday, will need to be extended.
Contact tracers are scrambling to track down infected people and have so far placed more than 1,000 of their close contacts in quarantine.
The lockdown has forced many in Queensland and interstate to cancel their Easter and school holiday plans.
Queensland's state economy is heavily reliant on tourism - and operators have forecast that the three-day lockdown has caused a A$35m (£19m; $26m) loss.