"We want to be practical about this, so parents and caregivers eligible [to be vaccinated] will also be able to book their [12 and over] kids."
Any parent already booked in could also take their 12+ child along at the same time.
"If you're already booked in then please just take them along. But please make sure that when you do, you work hard to keep social distancing [from others]."
Otherwise, those aged 12 and over can be booked from September 1, when the vaccine is available to everyone aged 12 and up.
"Please be assured we have more than enough Pfizer vaccine for everyone, including the 12 to 15 age group."
The vaccine was safe in the newly expanded age group, University of Auckland associate professor Helen Petousis-Harris said.
Its use had been studied in the 12 to 15-year-old age group and already rolled out to people of that age overseas, the vaccinologist said.
"It's extremely effective and has been shown to be extremely safe. This [age reduction] is part of the natural progression [of the vaccine rollout].
"And this group now, with Delta, it's highlighting that we're seeing more cases, and perhaps seeing more serious effects [in this age group]."
Because the virus had predominantly been more dangerous for older age groups some people believed young people were "completely immune" to serious illness and death if infected, which wasn't true, Petousis-Harris said.
"All along there's been young people hospitalised, and deaths, but the rates are much lower [than for older people]."
A phased approach to re-opening vaccination sites - closed temporarily when the level 4 lockdown began - also began today, Ardern also said during today's 1pm briefing.
Not all vaccination sites will be up and running today because some couldn't operate safely under alert level 4.
If you have a booking, and had no communication from provider, please still go, she said.
