Additional safety checks on the Covid-19 Pfizer vaccine for children create the long timeframe for the rollout, says an immunologist.
In the next two to three weeks, Medsafe and technical advisors will be looking to provide advice on the safety, efficacy and rollout of the vaccine for children.
However, even if the advice comes in with a recommendation for approval then, it would not be until the end of January that tamariki will start getting vaccinated.
University of Otago immunologist Dianne Sika-Paotonu told Morning Report while many would have preferred an earlier rollout, it was important to note proper checks are needed.
"This does take time... In New Zealand we do have layers to be worked through, and this includes Medsafe, the government's technical advisory group, but also Cabinet, so we need to be ready and prepared," Dr Sika-Paotonu said.
"Things did change with the Delta variant ... which showed a definitive shift from those within the older age bracket to the younger individuals actually becoming more seriously unwell, ending up being hospitalised, and dying from Covid-19," she said.
"The research took time because the clinical trials that were initiated began in adults.
"So proper tests and data and evidence needs to be made available to ensure the appropriate safety checks can be undertaken to give approvals after meeting really high standards."
The Pfizer vaccine dose for children was about a third of the adult one, and the evidence showed it was safe and generated a strong immune response, she said.
Working to finer details, like consideration body weight versus age, also contributed to the longer timeframe for approvals, she said.
Officials had no plans yet to pull the timeframe forward for the vaccination of children, but it was still under advice, said Director-General of Health Ashley Bloomfield.
There are enough vaccines to do this whole population group, Bloomfield said, but they would be make a big effort to go and vaccinate Māori and Pasifika tamariki early.
"The key reason for that is they tend to live in bigger households. And we know that household size does have a real impact on kids being infected inside the house."
Dr Sika-Paotonu agreed that those who were more vulnerable and compromised should be prioritised.
"Prioritisation is important because we've already seen what can happen if we ignore the evidence and don't undertake a corresponding action."
Of the current Delta outbreak, 20 percent of cases were aged nine years and under.
"Although children are more likely to have mild or asymptomatic disease, they can still catch the virus and become unwell, but they can also get better really quickly," Dr Sika-Paotonu said.
"However, they can end up with a long Covid-19 condition and for children and youth with underlying medical conditions, they do have a much higher risk of serious illness and hospitalisation."