With New Zealand's long-awaited child vaccine roll-out about to get underway, science reporter Jamie Morton recaps what parents need to know about the Covid-19 paediatric shot.
Why do we need to vaccinate young children?
It's an enduring myth of the pandemic that young children aren't affected by Covid-19.
The global experience shows that isn't true: in the US, for instance, children have accounted for around two in 10 Covid-19 infections.
Here, children aged under 9 have made up roughly the same proportion of all Delta cases – some infants among them – since the outbreak began last year.
While children are much more likely to have fewer or milder symptoms of the virus than adults, that didn't mean some couldn't become severely sick – especially if they suffered pre-existing conditions.
As at October, the US reported more than 8,300 hospitalisations among children, and nearly 100 deaths – placing it among one of the top 10 causes of death for kids aged 5 to 11.
The risk was also highlighted in an international study published this week, which tracked more than 10,300 children at 41 emergency departments in 10 countries, including New Zealand.
Around 23 per cent were hospitalised for treatment, and three per cent suffered severe outcomes - like heart complications such as myocarditis, as well as neurological and respiratory issues – within two weeks of their visit to ED.
Researchers are still learning about other complications being seen in children with Covid-19, such as multi-inflammatory syndrome and persisting symptoms known as Long Covid.
Globally, cases among children have been growing, something that's partly been blamed on lower vaccination rates, as well as the much higher transmissibility of Omicron.
It's still not clear what the new variant means for children: while the bulk of cases reported by doctors worldwide appear to be mild, there are some concerns it may be causing a harsh, barking cough known as croup.
The emergence of Omicron also highlights another reason to vaccinate kids – they can transmit the virus to others in their household bubbles.
One 2021 study found younger kids may even be more effective at passing the virus to caregivers and siblings than older children in their mid-teens.
Experts have also warned a surge in child cases could worsen health inequity in New Zealand, particularly among Māori and Pasifika communities who've already been hit hard in previous outbreaks.
By being vaccinated, childrens' immune systems could be prepared to fight off a Covid-19 infection much more effectively, said Dr Danny Delore, a Rotorua-based paediatrician and senior lecturer at the University of Auckland.
"This reduces the chance that a child would need to be admitted to hospital or ICU. Also, higher vaccination rates in the community helps to slow the spread of Covid-19," Delore said.
"This is important for children because it helps keep the adults in their lives healthy and it helps keep services that they need, like schools and medical services, up and running."
How can parents be assured the vaccine is safe and effective?
The vaccine used for tamariki is a children's version of the Pfizer vaccine, with a lower dose and smaller volume.
Well before our regulator Medsafe assessed the paediatric vaccine against its strict standards for safety, efficacy and quality, it had already been evaluated and approved by major agencies overseas.
They include the US Food and Drug Association (FDA), which considered a clinical trial involving around 3,100 children aged 5 to 11, and which detected no serious side effects.
University of Auckland vaccinologist Associate Professor Helen Petousis-Harris said that, while the numbers in those trials were relatively small, we could now draw on data from the many millions of doses since given worldwide – including nine million in the US.
"As with older age groups, there have been some reports of myocarditis but at substantially lower rates," she said.
"The current estimate for this potentially serious event in the 5-11-year-olds is around four per million doses and relatively mild."
Overall, common reactions such as feeling tired, having a headache, occurred less in the younger children compared to 12 to 15-year-olds.
"The vaccine is very safe in children."
The Ministry of Health also received regular advice from science experts in its Covid-19 Vaccine Technical Advisory Group (CV TAG), which recommended the use of Covid-19 vaccines in different age groups.
Clinical trials have also shown how Pfizer's paediatric shot performed well in children aged 5 to 11, with 90.7 per cent efficacy at preventing Covid-19 symptoms.
How and where will vaccines be administered to children, and why is an eight-week gap being proposed?
More than half a million doses of the vaccine arrived in the country this month, ahead of a roll-out covering some 476,000 eligible children across the country.
From Monday, the vaccine will be available for free at all the same places that provide the adult vaccine: parents will be able to access walk-in clinics, or use BookMyVaccine to use other health providers.
While there are no plans for a school-based immunisation programme, schools are being considered as community vaccination sites.
A parent, caregiver or legal guardian will need to accompany the child to their immunisation appointment and provide consent for them to be vaccinated.
As with adults, children need two doses of the vaccine to be fully protected, and the ministry recommended these be given at least eight weeks apart - although the interval could be safely shortened to a minimum of 21 days if needed.
"This is being recommended because it's expected from first principles to give a better antibody response, and to allow time to have as much safety data on dose two as possible," explained Professor Peter McIntyre, an Otago University paediatrician and Immunisation Advisory Centre medical advisor.
"But in the meantime, this age group overall have a very low risk of severe disease - and we would expect one dose to give good protection against severe disease at least in the short term."
The second dose was mainly to "bump up" antibodies to protect against milder infections.
"The second dose increases the immune system's ability to fight off Covid-19, but if you give the dose too soon the immune response isn't as strong," Delore added.
"Eight weeks was chosen as the sweet spot between maximising the strength of the response without delaying the benefits of full vaccination too long."
How should I talk to my children about the vaccine?
Otago University immunologist Dianne Sika-Paotonu suggested parents simply tell their kids it's time for another vaccine – just like those they'd had before.
"It might be helpful also to point out that the vaccines they've been given in the past have stopped them from becoming seriously unwell, and so have kept them safe and protected," she said,
"Pointing out that this is how vaccines in general work, by giving protection from serious illness, will be useful."
As well, parents could make it clear to their children that they'd been vaccinated too, and that all kids would be getting the same vaccine.
Delore recommended keeping the conversation "simple and honest".
"Explain why the vaccine is important, and that vaccination is a normal part of keeping healthy, but don't make the event into something bigger than it needs to be," he said.
"Talking about it for a long time can make them worry more – so tell them the vaccine will sting when it goes in, but it's all over in a flash. Tell them you'll be right next to them."
"Avoid enticing children with rewards or entering into negotiations, but let them have some control over simple choices, like which arm the vaccine will go in."
The ministry advised parents to ensure their children had had something to eat and drink before receiving their vaccine, and to bring a distracting item like a soft toy if they felt nervous.
The woman was shaken by the incident.