"So what the data is telling us in the last few days is that we haven't seen the worst of it," Premier Gladys Berejiklian said on Wednesday.
"According to the data we have every person who has the virus spreading it to at least more than one person."
The isolation status of 447 cases in the 24 hours to 8pm on Tuesday remains under investigation.
The previous NSW daily high was 478 cases reported on Monday.
Young people living in Sydney's worst COVID-hit areas can now book to get a Pfizer jab during a two-week vaccination blitz designed to drive down transmission in those hotspots.
Those aged 16 to 39 living in the 12 local government areas of concern will be given priority access to the Pfizer vaccine at NSW Health clinics from Thursday.
Ten government vaccination clinics have ramped up their capacity to deliver the additional 530,000 doses provided by the federal government to the priority group over the next two-and-a-half weeks.
The entire state is locked down with tight restrictions but authorities are concerned that 70 per cent of transmission is occurring in homes.
The likelihood of household transmission is reduced by about 50 per cent by three to four weeks after vaccination.
Deputy Premier John Barilaro says the government is also bolstering vaccination efforts in western NSW with 116 COVID cases there and concerns about vulnerable Indigenous communities, with cases expected to spike.
He admitted that mistakes had been made with the Sydney lockdown that began eight weeks ago.
"Well, look, I think if you can rewrite history we could have gone harder," he told the Nine Network.
Meanwhile, Orange MP Philip Donato has lashed the state government for redirecting Pfizer vaccines from the regions to Year 12 students in Greater Sydney.
He's received a flood of messages from constituents, including frontline health workers and vulnerable people, who've had their vaccination appointments cancelled.
"It was foreseeable that regional NSW was increasingly vulnerable to Delta, and given the insufficient health services across the west, the potential outcome was more dire," he said in a statement.
"Given the premier's poor and inconsistent management of Delta outbreak in Sydney, blind Freddy could see that COVID-19 was going to find its way into the communities of regional NSW."
Most of the locals surveyed said their cancelled appointments were yet to be rescheduled, while others will have to wait up to nine weeks, he said.
Australian Defence Force members will join Dubbo and Newcastle police from Wednesday to help with welfare doorknocks and compliance checks.
Some 50 personnel will be deployed in each region with more expected by the end of the week.
NSW Health has also clarified that people can attend a gravesite for compassionate reasons such as an anniversary of a dead child or following a recent death of someone close.
Under the public health order, cemeteries are not required to close and attending a funeral or memorial service is a reasonable excuse to leave home, with a maximum of 10 people allowed to attend in Greater Sydney.
BreastScreen NSW announced on Tuesday it would suspend all routine breast screening across NSW because of the outbreak.