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Yes, we’re going there – Should you vaccinate your child?

It’s always a good time to talk about vaccination – but the issue is in the news now with Labour floating the No Jab, No Play policy from Australia so we’ve decided to go there.

Vaccination is always something you have to think about when you’re a parent – should you? Shouldn’t you? Lots of people have opinions and it’s confusing. I didn’t think too much about vaccination before having a child. I knew I would because it made sense too. But then I had a child with a serious health condition. Suddenly I had to advocate for him so I had to become vocally pro-vaccination. Late at night I would sit and cry reading mothers in Facebook groups convince each other not to vaccinate. They would say things like – “Whooping cough is just a cough” and “some kids just aren’t meant to survive, I shouldn’t have to put my child at risk for their child”. I’d read these things and feel like I lived on another planet. A simple cold caused my son’s trachea to collapse and he ended up in emergency surgery – and they were saying whooping cough was just a cough. There is a huge group of mothers weeping over comments that say “my child’s body, my choice”. We sit in hospital wards staring at our babies and hoping and wishing someone will come along and properly explain that this is a choice not made in isolation. It’s a choice that impacts vulnerable children and adults. It’s a choice that says to all parents, but especially those of us with medically fragile children, that our children are loved and valued too and that their lives matter.

But I accept that it’s scary to give your child any kind of medical treatment. My son had so many necessary medical procedures in his first few months, surgeries too before he was two. It’s harrowing. To this day I hope I made the right choices with some of his care. My husband and I made our choices based on the advice of a team of doctors – we trusted them. We needed to trust them. We saw them save our son’s life so why wouldn’t we? We talk about health privilege further in this podcast. This post looks at the evidence without the emotion. Something I can’t do. It looks at risk too because of course there is risk. It’s the first in a two part series on immunisation by our resident evidence-based scientist Dr Jess, someone who actually can talk about vaccination without resorting to inaccurate scaremongering blogs. Because you need clear and factual information about immunisation – and that is what this post will give you.

So there’s your context, here’s part one:  Why Childhood Immunisations are an Awesome Way to Take Care of Others. When moderating on Facebook we will not allow misinformation on vaccination to be posted. It puts lives at risk and is against the kaupapa of the Spinoff Parents which is about supporting families.

Emily Writes, Editor, The Spinoff Parents

Widespread immunisation helps everyone

A vaccination prevents an individual getting a disease that much is pretty straightforward [1]. Once a vaccination is administered then the body responds to the vaccination to make the individual immune to a disease. However, widespread immunisation also has benefits. If enough people are vaccinated it eventually makes enough people immune that it eliminates a communicable disease (a disease you can catch from someone else who has the virus) in a community, a society and eventually worldwide. Smallpox for example is eradicated worldwide.

This is known as “herd immunity”: when enough people are fully immunised (for most vaccines this is near 95% of the population), the risk of someone catching the disease and passing it to someone else not immunised is very low. Eventually the disease cannot continue to live as it cannot find enough hosts for it to breed in, and it becomes extinct. If only we could do that with rats and possums so effectively!

A vaccination comes with risks

As I have talked about in Good Science it is important to understand that no medical treatment is without risks. Having an ingrown toenail removed has a risk of toe amputation, having a general anaesthetic has a risk of brain damage.

But with most interventions the likelihood of the most severe side effect is much smaller than the risks associated with not doing the thing. So there are some risks when a child is immunised, for example inflammation at the site of the injection or fever. There are even smaller risks of some more serious side effects like an allergic reaction called anaphylaxis. However, such severe side effects occur much less often with the vaccine than they would if a person caught the disease itself.

The figure below compares the risks of having the MMR (Measles Mumps Rubella) vaccine vs. taking your risks with measles. If a million children had the vaccine, and another million caught the disease, then we would expect to see the numbers of complications in the table below.

Figure 1. Severe complications due to MMR vaccine and measles among 1 million children aged under 5 years. Source:  The Australian Academy of Science.

What we can say is that there is NO risk what so ever that you will get autism from a vaccine.

This creates a prisoner’s dilemma

A what?

Well as immunisation rates grow in a society (as they are currently in New Zealand), the risks of contracting a disease lessen, as do the overall risks in a population of being hospitalised or dying from that disease. So if enough other people are immunised, then it might be rational for some people to take the risk and choose not to vaccinate their child. In other words, if the chances of their child contracting the disease are low, the parents might choose to avoid the (also low) risks associated with getting the vaccination.

Example of a Prisoners Dilemma

For simplicity lets pretend a community has two undecided and unrelated parents, Andrew and Brian. They have herd immunity explained to them, alongside the risks of the vaccination for measles, the risks of contracting the disease and the risks of hospitalisation or death if their child gets the disease.  Each are then asked to decide whether to vaccinate their child against measles. The risks and rewards for them are as follows:

  • If Andrew and Brian both don’t vaccinate, each child has a higher risk of contracting the disease and of experiencing serious health effects of the illness, but they avoid the risk of vaccination side effects.
  • If Andrew does not vaccinate but Brian does, Andrew’s child will have a lower risk of catching the disease, low risk of experiencing serious health effects of the illness and no risk of vaccination side effects. Brian’s child will have a low risk of the disease, low risk of experiencing serious health effects of the illness and some risk of vaccination side effects (and vice versa). In short, Andrew is taking a ‘free ride’, benefitting from Brian’s choice to immunise his child.
  • If Andrew and Brian both vaccinated, both children will have the lowest risk (becoming no risk) of the disease and experiencing serious health effects of the illness, while both children have a risk of vaccination side effects.

Assuming Brian vaccinates his child, it might make sense for Andrew to choose not to. And this applies in the real world – in a mathematical sense the truly ‘rational’ parent (when understanding the real scientific risks, we are not talking myths here) may choose not to vaccinate, provided that enough of society has been vaccinated to provide herd immunity. ‘ However, eventually this would backfire on everyone the rational parent included.

Why the ‘Free-Riders’ are hurting their kids (and others) in the long term.

You can probably see the problems in this ‘rational’ but ultimately kind of selfish decision-making process, and not just for the wider community as a whole. In taking this ‘free ride’, parents who choose not to vaccinate could actually be harming their child in the longer term. As the vaccination rates decline (as more people choose not to vaccinate believing the risk to be low) the actual risks of contracting the disease then rise. So every child is now exposed to a greater level of risk, BUT especially those that are unvaccinated.

How do we know this? Because in countries with low vaccination rates, their rate of disease is at epidemic proportions. This interactive map shows where measles is at an epidemic rate worldwide – the majority of deaths from measles are in children under 5. Afghanistan which has an immunisation rate of less than 40% had 6000 cases in 2012 (likely to be more due to poor reporting mechanisms).

And just in case you think this is a developing world problem, in New Zealand in 1991 our immunisation coverage rate at 2 years was less than 60% overall, and only 42% In Maori and 45% Pacific children[2] . In 1997 we had a large scale measles outbreak, there were 2169 cases notified, near 100 people hospitalised and 7 people died, four of those who died were children who were not immunised (Ministry of Health Immunisation Handbook, 2014). As we will see in part two, even now we don’t have the levels of immunisation we need for herd immunity – so any parent not vaccinating their child is rolling the dice with disease.

If an unimmunised child does come in contact with measles for example, there is a 90% chance they will get it, and if they do get it there is a 1 in 5 chance they will be hospitalised for serious complications and a 1 in 1000 chance they will die. So if increasing numbers of parents choose not to vaccinate due to a low risk of disease they are actually, ironically, increasing the risk of their child becoming seriously ill during outbreaks. What is almost worse is that they are putting some already really vulnerable kids at greater risk.

Free-riders risk making sick & vulnerable children sicker

For children with compromised immunity, and in New Zealand this is mainly children and babies receiving chemotherapy treatment for cancer, or with immune system diseases, if they contract measles they have a 1 in 2 chance of dying from it. Young babies, who have undeveloped immune systems and are too young to get a vaccination, are at high risk of contraction and hospitalisation during an outbreak of a disease. Children in poverty who already suffer an additional disease burden compared to their better off counter parts, are more vulnerable also due to their lower vaccination rates (an issue we will go into in the next blog).  So as the rate of a disease increases due to a decline in vaccination rates, the kids that suffer from this decline are those that are least able to cope.

Only a few of us can have a free-ride and it needs to be based on need.

If herd immunity is achieved when 90-95% of the population are fully immunised (depending on the disease) and this rate is maintained for a period of time, then the 5-10% we can carry unimmunized in our society needs to be reserved for those with the greatest need, not those who want to opt out. It is like giving the wheelchair to someone with an ingrown toenail when there is a person with paralysis next to him or her in the queue.

It helps if information about the risks and benefits, both individual and population based, are communicated effectively and people are given the opportunity to understand that their personal decision affects everyone.


In summary, having your child vaccinated helps not only your child but also everyone in society. The risks from a vaccination are much lower threat the serious risks that come with the diseases we vaccinate against. It might seem a good idea, to some, to get a ‘free ride ‘ from the lower disease rates we currently experience and not vaccinate. However, this lower rate only exists because people vaccinate their children. Ultimately such free riding will put all children who are not immunized at greater risk, as disease rates will go up again.

So be bold, be brave, be community minded and do the right the thing, for your child, and others

In part two I will look at the broader state of immunisation in New Zealand situation and expand on why the most vulnerable in our society are the ones that lose out when people choose not to vaccinate.

[1] [1] Plotkin, S.A., Orenstein, W.A., and Offit, P.A. eds. (2007). Vaccine. 5th edition. Saunders Elsevier.

[2] Stehr-Green PA, Baker M, Belton A.  Immunisation coverage in New Zealand:   results of the regional immunisation  coverage surveys. Commun. Dis. NZ 92(Suppl. 2), S1–S17 (1992).

Dr Jessica Berentson-Shaw is a mother of two, scientist, writer, and author. This is her approach to writing about science for The Spinoff Parents.

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