The children's Covid-19 vaccine is being described as like an "insurance policy" giving protection against the low risk of becoming severely ill with the coronavirus.
Thousands of 5 to 11-year-olds have already had their version of the shot since the rollout started in Aotearoa yesterday.
University of Otago vaccine expert Dr Peter McIntyre said data continued to show the risk of Covid-19 for children was much lower than for adults, but a vaccine would save some children ending up in hospital.
He pointed to data from New South Wales that show around 0.4 per cent of 5 to 11-year-olds with Covid-19 were hospitalised - about 1 in 250 children. A small number of those ended up in intensive care.
"It's not that common, but it's the kind of thing you'd still like to prevent if you could. So you could think of it as an insurance policy. We all have car insurance, and we don't plan to have an accident, but it's really nice to have it if you do."
In New Zealand, 45 children aged up to 9 years old have been hospitalised with Covid-19, which is about six per cent of all hospital admissions for the coronavirus. None have been admitted to intensive care.
Australia started its children's vaccine rollout a week ago. The US began in November and has given more than eight million doses to children.
McIntyre said children with underlying health problems should get theirs as soon as possible.
Waitematā DHB paediatrician Dr Owen Sinclair said even though the illness was milder for children, being vaccinated helped protect others, for example their grandparents or immunocompromised family members.
"The vaccine will help with that web of protection. If you are vaccinated, you're much less likely to get it, and you're also much less likely to pass it on," Sinclair said.
"Children getting the vaccine just added up strongly to be a very good thing to do."
This "web of protection" was particularly important for Māori, he said.
"As a Māori, protecting your whānau is very important. It's the key to our existence and who we are. We argued heavily that if children were asked whether they would want to get immunised to protect their whānau then they would."
Some of the first under-12s in line for vaccination in Tāmaki Makaurau yesterday were pretty happy and said the jab didn't even hurt.
"It was just like my brother pinched my arm," one said. "Come down and have it," another said. "It's not too bad."
"I want to get vaccinated so I can keep playing my sports and keep myself safe and see my family," another said.
"I didn't even feel anything - I was talking and I turned around and she said she was done! I feel better since I got it done."
Clinical director of the vaccination programme for the Auckland area Dr Anthony Jordan said the first day was busy, and they expected that would continue over the next few weeks, before children went back to school.
With many adults becoming eligible for a booster dose, Jordan has an idea: for parents and children to get their dose at the same time.
"Definitely, we'd want to encourage that - so the whole family, whānau can come along. I think that sometimes can help too - it's really reassuring."
The vaccine for children is a lower dose and smaller volume version of the adults' Pfizer vaccine. Children need two doses to be fully protected, given at least eight weeks apart.