Scott Morrison has urged locked down Australians to receive a second AstraZeneca dose within eight weeks of their first jab.
The prime minister is making another bid to speed up the vaccine rollout with a focus on people in Sydney and surrounds.
Australia's largest city is in the grips of an ongoing outbreak, with NSW reporting 38 new local cases on Thursday.
Mr Morrison encouraged people who had received a first AstraZeneca jab to move their second dose appointments closer to eight weeks.
"Given the risks to people of the outbreak in that area, we believe it's important that they get that second dose of AstraZeneca as soon as possible," he told reporters in Sydney on Thursday.
In the three Sydney councils with the most infections, about half of those aged over 70 have received a first dose.
While 12 weeks is the preferred gap for AstraZeneca jabs, the medicines regulator has approved it for use within four weeks of the first dose.
Some experts have warned effectiveness is reduced with shorter gaps.
Mr Morrison said his latest comments were consistent with the advice of the expert immunisation panel.
The prime minister was last week accused of launching a "hand grenade" into the rollout when he used a late-night news conference to highlight a path for under-40s to receive AstraZeneca.
An extra 300,000 AstraZeneca - which is recommended for people over 60 - and Pfizer vaccines will be made available for NSW.
More people in Sydney and surrounds will be eligible for $325 to $500 weekly federal disaster payments in the third week of lockdown with the $10,000 liquid asset test to be dropped.
Mr Morrison is under sustained pressure over the vaccine rollout, with little more than 10 per cent of people aged over 16 fully immunised.
Labor leader Anthony Albanese continues to target the decision not to have a more diverse vaccine portfolio.
"They have completely botched the rollout of the vaccine and national quarantine," he said.
The prime minister argued the program was on track to be just two months behind its original targets if all Australians were offered a jab by year's end.
"The vaccination rate that you're seeing right now and what might otherwise have been the case at this stage would have still required a suppression strategy right now," he said.
"To suggest otherwise is just completely and utterly false."
Health Minister Greg Hunt is optimistic additional Pfizer supplies could arrive next month with confirmation expected in coming days.
There are calls for Australia to use its close alliance with the United States to secure more Pfizer doses sooner.
The Biden administration is exporting Pfizer and Moderna shots to Canada and Mexico, while also sending supplies to Brazil and Taiwan, and promising doses for Indonesia.
When asked if he had been in talks with the US government, Mr Morrison pointed to deals with Pfizer to increase Australia's allocation.
Labor's foreign affairs spokeswoman Penny Wong said Australia should look at all options for more supplies.