Image: Getty Images, additional design by Archi Banal
Image: Getty Images, additional design by Archi Banal

ScienceJanuary 17, 2022

All your questions about kids and Covid vaccines, answered

Image: Getty Images, additional design by Archi Banal
Image: Getty Images, additional design by Archi Banal

From today, children in New Zealand aged 5 to 11 can get the Covid-19 vaccine. Siouxsie Wiles, Jin Russell and Helen Petousis-Harris – experts on Covid, child health and vaccines – got together to answer some of parents’ most frequently asked questions.

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Is there a difference between the adult and child Pfizer vaccines? 

Yes. There are two main differences. 

The first difference is in the amount of active ingredient, which is the mRNA for the Covid-19 virus’s (S) glycoprotein. The adult vaccine has 30 micrograms of mRNA while the child vaccine has 10 micrograms. Children are given a smaller dose not because of their smaller size but because of their more active immune systems. Ten micrograms is the amount that was found in the clinical trials to stimulate children to produce an antibody response that was the equivalent of people over 16. 

As well as the mRNA, both Pfizer vaccines contain three other types of ingredients: fats, salts and sucrose. Sucrose is a sugar that is added to protect the other ingredients at the very cold temperatures the vaccine is stored at (-80 degrees C). The fats make up the lipid nanoparticle coat which helps to transport the mRNA into our cells without it being broken down. These are the same in both vaccines and have long chemical names: (4 hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-distearoyl-sn-glycero-3- phosphocholine, and cholesterol. These fats are also used to deliver lots of other medicines. 

The second main difference between the child and adult vaccines are the ingredients that help ensure the vaccine is at a similar pH to that of human cells. In the adult vaccine, these are a bunch of different salts: sodium chloride, potassium chloride, monobasic potassium phosphate, and dibasic sodium phosphate dihydrate. In the child vaccine, they’ve kept the sodium chloride but replaced the others with tromethamine and tromethamine hydrochloride. Tromethamine is a well-used medicine in humans as it is given to people to treat metabolic acidosis, a condition where too much acid accumulates in the body. The only reason they have been put into the vaccine is to make the vaccine stable for longer when it’s stored in the fridge.


Charles Muro, age 13, celebrates being inoculated in Hartford, Connecticut on May 13, 2021 (Photo: JOSEPH PREZIOSO/AFP via Getty Images)

Is it safe? How do we know? What do we know about adverse reactions in kids?

Right now, we have two bits of data to help answer these questions, the results of the clinical trial and the data that is accumulating now that the vaccine is being rolled out in different countries. The first report from the trial is here. It involved 2,268 children from Finland, Poland, Spain, and the USA. Of those, 1,517 were randomly assigned to receive two doses of the Pfizer vaccine three weeks apart and 751 received a placebo. 10.9% of the vaccine recipients reported an adverse event compared to 9.2% of the placebo recipients. Severe adverse events were reported in 0.1% of the vaccine recipients and 0.1% of placebo recipients. The main difference between the two groups was that more children in the vaccine group (0.9%) reported having swollen lymph nodes under the arm compared to children in the placebo group (0.1%). This is not at all surprising, as swollen lymph nodes are a sign of an immune system hard at work. There were no reports of myocarditis, pericarditis, hypersensitivity, or anaphylaxis.

While the trial data is really important, there are too few participants to tell us about adverse events that could be rare. For this we need much bigger numbers of people. We are starting to get a lot more information about the safety of the children’s vaccine from the real-world data. Between 3 November and 19 December 2021, 8.7 million doses of the vaccine were given to 5-to-11-year-olds in the USA. Just like here in New Zealand, the USA has a system for people to report any potential side effects from vaccination. Their system is called VAERS – the Vaccine Adverse Event Reporting System. The CDC recently published an analysis of the VAERS data and it is good news. Firstly, from those 8.7 million doses there were just 4,249 VAERS reports of which almost all – 97.6% – were classified as not serious. They were mostly for errors with how the vaccine was stored or prepared or for side effects like fatigue or headaches. 

Just 100 of the VAERS reports were classified as serious. There were no deaths related to the vaccine. Most of the serious VAERS reports were of children experiencing fever and/or vomiting after being vaccinated. There were 12 reports of children having a seizure. The big one everyone is probably thinking about is myocarditis – inflammation of the heart. The VAERS data shows it’s very rare with the children’s vaccine. There were just 15 reports, of which 11 were verified. At the time of the CDC analysis, seven of the children had already recovered and the other four were recovering. 

While systems like the VAERS are really useful for detecting unexpected safety signals, there are other approaches that go looking for adverse events. One example is called the Vaccine Safety Datalink (VSD) and this system looks at medical records such as doctor visits and hospitalisations and whether or not a person has been vaccinated. The VSD  has millions of people, included including 848,000 children aged 5-11. It is very useful for seeing if a vaccine increases the risk of a particular adverse event, or not. The VSD is looking very closely at the data for children receiving the Pfizer Covid-19 vaccine. So far they have data for 431,000 doses and have found no safety signals. There are other systems like this across the world.

In other words, both the trial data and the real-world data are showing that the Pfizer children’s vaccine is very safe. 

Is the vaccine as effective in kids as it is for adults? How protected are they after the first dose?

There doesn’t seem to be any analysis of the real-world data available yet, but the data from the clinical trial showed the vaccine was protective. This is the relevant graph – it shows that as the study progressed, more children in the placebo group contracted Covid-19 than in the vaccine group. The data put the efficacy at about 90% which is just a little lower than for the adult Pfizer vaccine in clinical trials. They just looked at infections that happened at least seven days after the second dose so we don’t have any data on how protective one dose is yet. 

A 7 year-old child holds a sticker she received after getting the Pfizer-BioNTech Covid-19 vaccine in Michigan, on November 3, 2021 (Photo: JEFF KOWALSKY/AFP via Getty Images)

Why is the gap between vaccines eight weeks and not six weeks? If your child has a disability or “comorbidity” should they have a shorter gap?

These are good questions. The trial tested a gap of three weeks between doses. The Ministry of Health’s vaccine advisory experts set the gap at eight weeks as that length of time between doses is similar to what is done for other childhood vaccines and is likely to result in better immunity. 

For some children it may be appropriate to shorten the gap. The best thing to do is to talk to your child’s GP or specialist for advice. There is also some good info on the KidsHealth website

My child turns 12 in March, should she wait to get the adult dose?

No. It’s better to get them vaccinated sooner rather than later.

Will my kid need a booster?

There are two reasons boosters might be needed – if the immune response after vaccination wanes over time, or if the virus changes in a way that the vaccines provide less protection. We’ve seen both these things happen so far with the adult vaccine and the emergence of omicron so it wouldn’t be surprising if more than two doses are going to be needed. Lots of the current childhood vaccines are more than two doses so this isn’t unusual. We should find out more in the coming months.

There are so few cases in the community right now. Should I hold off getting my kid vaccinated so their peak immunity is higher when there’s an outbreak?

No. Please get your child vaccinated now. When an Omicron outbreak is identified, the variant may have been circulating in the community undetected for a little while. It takes our bodies two weeks to build up good immunity after being vaccinated, and with the doses currently being eight weeks apart, it’s best to start the process sooner rather than later. 

Should children with disabilities or comorbidities wait until they’re fully vaxxed to go back to school?

Most children with disabilities and comorbidities would do well not to delay going to school as school is so important for children in many ways. In adults, a single dose of the Pfizer vaccine can still confer protection against hospitalisation up until the second dose is given, so there is no reason to think the children’s vaccine wouldn’t do the same. Remember also that vaccines are just part of the way we protect people from Covid-19. Masking, ventilation, and air purification are really important for minimising transmission of the virus and we should be using these measures in schools. 

If kids get vaccinated now, will they still have immunity come winter?

Yes. At the moment the two doses are being given eight weeks apart. That means children that are vaccinated this week will be fully immunised by the beginning of April so will have good levels of immunity going into winter.

A child receives the Covid vaccine on September 18, 2021 in Phnom Penh, Cambodia. (Photo: Cindy Liu/Getty Images)

Aren’t only a few countries vaccinating under 12s? How do we know it’s a good idea?

Lots of countries are already vaccinating under 12s or will be shortly including the USA, Canada, Singapore, Cuba, Venezuela, Argentina, Chile, El Salvador, Costa Rica, Ecuador, Israel, Oman, Saudi Arabia, Bahrain, and the United Arab Emirates. Many, but not all, will be using the Pfizer vaccine. The European Union have also approved the Pfizer vaccine for 5-11 year olds, but countries in the union will decide for themselves whether to use it. So far, Spain, Italy, France, and Germany are vaccinating or plan to vaccinate under 12s. 

Isn’t Covid usually mild in kids? Then why get them vaccinated?

Children with Covid-19 infection generally experience a mild illness. Many are not even aware that they are infected because they have no symptoms and don’t feel any different. But Covid-19 can be unpredictable and a small proportion of children can be sicker. Australian studies show that approximately 1 in 100 infected children need to be seen in hospital for review, fluids, or oxygen. Fortunately these hospitalisations tend to be brief. 

Approximately 1 in every 3000 infected children develop a rare but more serious complication called multi-inflammatory syndrome in children (MIS-C) which comes on several weeks after infection. Children with MIS-C can need intensive care. MIS-C is most commonly seen in the 5-11 year age group. We also want to protect children from persisting symptoms after Covid-19 infection – also known as long Covid.

Vaccinating children also helps protect their whānau, other children with pre-existing conditions, and their communities. 

The delta variant is still circulating in New Zealand. In the Pfizer trial, two doses of the Pfizer vaccine were 91% effective in preventing symptomatic infection. In adolescents aged 12- to 18-years-old, two doses of Pfizer is estimated to be 91% effective in preventing MIS-C, 94% effective in preventing hospitalisation, and 98% effective in preventing intensive care admission, and it is reasonable to expect similar protection in 5-11 year children.

My son is terrified of needles. Any tips?

It helps children who feel anxious to have a calm grown-up with them as children regulate themselves according to their parents. Planning ahead helps. Being vaccinated at a familiar place, like the local GP clinic, may help. Some children prefer the safety and snugness of being in the car, so a drive-thru clinic may be better. Do tell the vaccinator first what helps your child.

The best approach is to be honest in a matter-of-fact way with children about what to expect. Before getting vaccinated, tell children that it is a very short needle and that there is a “sting” or “scratch” but then it is over very quickly. 

Make sure children have had something to eat and drink first so they are at their best. They may prefer to go early in the morning so they are not worried about it all day. Young children may want to bring a soft toy for comfort. 

Have some options for holding your child so that they are upright. Some younger children like to sit on their parents’ laps facing forwards, or facing their parents in a bear hug. 

It helps for children to be distracted. Make a plan beforehand. Some children like to have their back or shoulder rubbed, look at a picture, talk about something else, listen to a song, watch a short video on a cellphone, as a distraction.

After it’s done, give them lots of specific praise! Make plans to do something fun to celebrate afterwards and talk about what went well.

The majority of anxious children do well with the strategies above. For children with needle phobia – an overwhelming fear of needles – a topical anaesthetic cream (e.g. Emla 5% cream) can help. This can be prescribed by a doctor or purchased over the counter at the pharmacy and rubbed on half an hour beforehand. More information on managing needle phobia can be found at the IMAC website

For more advice on kids and needles, read the tips from Emily Writes’ son Eddie, who as a diabetic is something of an expert on dealing with injections.

Photo: Getty Images, additional design by Archi Banal

Will the vaccination centres be handing out lollipops?

Not sure about that, sorry! It will probably depend on the vaccination centre. If you know a lollipop afterwards will help, then take one along with you in case they don’t have anything. It would be great if they handed out badges to wear showing you’ve been vaccinated. That’s a reward that lasts much longer than a lollipop!

Any advice for neurodiverse kids?

A lot of the suggestions made to help anxious children also help for neurodiverse children. On top of that, neurodiverse children do better with social stories (a story with pictures that describes being vaccinated) beforehand to tell them what to expect. 

There is a disability team which is available to support you and your child to be vaccinated. Either tick the box for extra support when booking at the bookmyvaccine.nz website, or call the Covid Vaccination Healthline team 8am – 8pm, 7 days a week on 0800 28 29 26.

Is the needle smaller for kids? 

The needle is the same small needle that is used to vaccinate babies and toddlers. This needle is also used for adults.

Are there any helpful resources I can show my kids to help ease their anxiety?

You can show them this video by Toby and Siouxsie which shows how vaccines work and how using them is like part of a multi-player game.

There are also some great resources on the KidsHealth website, including lots of short interviews with paediatricians. This page especially is full of all sorts of useful things. You could also check out this webpage from the Children’s Hospital of Philadelphia which has all sorts of vaccine resources for children. 

My friend/sibling/partner is reluctant to get their kid vaccinated. How should I talk to them about it?

The Workshop has a great resource for talking to people about vaccination. Check it out here.

Do you think vax mandates for kids clubs, sports etc. are a possibility?

It’s unlikely the government will mandate something like this. But it is certainly possible that individual clubs and groups will bring in policies requiring vaccination to protect their more vulnerable members.

About the authors:

Dr Helen Petousis-Harris is a vaccinologist and associate professor at the University of Auckland. Her main research areas are vaccine safety and vaccine effectiveness and she is currently co-leading the Global Vaccine Data Network, a multinational consortium dedicated to collaboration in vaccine safety studies.

Dr Jin Russell is a developmental paediatrician in Auckland, and a PhD student in life-course epidemiology at the University of Auckland. She is a former member of the NZ Policy and Advocacy Committee and College Council of The Royal Australasian College of Physicians.

Dr Siouxsie Wiles is a microbiologist, associate professor and head of the Bioluminescent Superbugs Lab at the University of Auckland, and one of New Zealand’s leading voices on the Covid-19 pandemic. She is the 2021 Te Pou Whakarae o Aotearoa Kiwibank New Zealander of the Year.

The Spinoff’s science content is made possible thanks to the support of The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.

Mad Chapman, Editor
Aotearoa continues to adapt to a new reality and The Spinoff is right there, sorting fact from fiction to bring you the latest updates and biggest stories. Help us continue this coverage, and so much more, by supporting The Spinoff Members.Madeleine Chapman, EditorJoin Members

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