The Risks And Benefits Of Vaccination
And the reason we vaccinate
There are lots of arguments going on about vaccines. Partly this is because vaccines have always been controversial, from when Jenner first tried sticking lumps of flesh in children to prevent smallpox — amazingly, it worked — to the more modern vaccine resistance that’s going viral today*.
And it’s no wonder that people have questions. Vaccines are scary. I wince every year when I get my flu vaccine, and it’s not just the frigid air of the ward air conditioner on my bare nipples. It’s a bit unnerving to get a shot, and even though I know all the science behind the decision, have studied this and know it’s safe, there’s always that slight moment of doubt nevertheless.
Even more terrifying when it’s your baby getting the injection.
So it makes sense that one of the biggest questions that comes up time and again about vaccines is about risk. The idea goes that vaccines have risks, and that makes them unsafe. Therefore, we should not vaccinate babies, or vaccinate less, or give certain vaccines a miss.
The problem with this argument is that it almost always involves wildly overblowing the risks, and ignoring the benefits.
We vaccinate for a reason. You see, vaccines may be risky, but the alternative is far worse.
Vaccination Research
To look at vaccine risks and benefits, we have to start at the beginning. There are, broadly, two stages of vaccine research — pre and post licensure, or the period before and after a vaccine is licensed and sold. Pre-licensure studies mostly look at efficacy and relatively common side-effects, because while they are very rigorous they are often not big enough to find truly rare side-effects. Post-licensure studies are there to find out if the vaccine is working as intended in the population that’s actually getting the vaccine, and whether there are any rare side-effects that the initial research couldn’t see.
Basically, pre-licensure studies make sure vaccines are safe and effective in best case scenarios. Post-licensure studies make sure that the findings of the initial research hold true in the real world.
So vaccines are studied a lot, both before and after they are released to the public. A large focus of this research is on whether the vaccines are safe, because they are given millions of times a year to children, and we want to make sure that any possible harms are as unlikely as possible.
No one wants babies to be sick.
What do the results of all this research show?
Risks And Rewards
The combined measles, mumps, and rubella (MMR) vaccine is a good case-study in vaccine risks and rewards. It’s one of the most discussed vaccines, and also one of the most studied.
First, let’s look at the risks.
There have been quite a few studies over the years that look at risks following MMR vaccination. If we turn to the gold standard of evidence here — a large systematic review by the Cochrane collaboration — we can see exactly what the risks are**.
The most common serious side-effect of the MMR vaccine is what’s known as a febrile seizure. This is a short seizure caused by a high fever brought on by the vaccine, and is scary but usually doesn’t have any long-term side-effects. The other serious side-effects of MMR are anaphylaxis and — for a specific strain of the vaccine — meningitis. These side-effects are much, much rarer, but also more serious.
Overall these side effects cause about 100 hospitalizations for every million children who get the MMR vaccine.
What about the benefits?
Well, all of these diseases are very infectious. In an unvaccinated population, virtually all kids will get measles, and most of them will get mumps and rubella as well. That’s because these diseases are very contagious, so they get passed around.
Measles is a very severe infection. Of the kids who contract the disease, about 1 in 5 will end up in hospital. 1 in 10 will have a serious ear infection that can cause deafness. 1 in 1,000 will get encephalitis, which can cause lifelong disability. 1–2 in 1,000 will die.
Mumps and rubella are not nearly as serious as measles, but even so can cause infertility, encephalitis, and hearing impairment.
Overall, about 1 in 4 children who get these diseases will end up in hospital because of it. The vaccine prevents up to 100% of disease once the herd immunity threshold is reached (like in Australia, where there hasn’t been an endemic measles case since 2014). Let’s do a quick calculation:
Risk of hospitalization due to MMR = 100 in 1,000,000 = 1/10,000 = 0.01%
Risk of hospitalization due to measles, mumps, rubella = 1 in 4 = 1/4 = 25%
What this means is that a child is roughly 2,500 times more likely to go to hospital because of an infection than they are due to the MMR vaccine. In absolute terms, children who are vaccinated are 25% better off.
In practical terms, every four vaccines stop one child from going to hospital, and every 500 vaccines save a child’s life.
Sounds like a pretty good deal to me.
Why We Vaccinate
Now, I’ve used the MMR as an example, but this is true for all the vaccines that we routinely give. Most vaccines have a serious risk rate of about 0.01%, whereas most diseases have risk rates hundreds of times higher than that.
That’s why we vaccinate. In a nutshell, nice and easy. Vaccines have risks, like any medical intervention, but they are really small. Diseases, on the other hand, have risks that are really big. In the modern era of wonderful medicine, disease risks can seem negligible, but it’s worth remembering that more than 100,000 people still die each year from measles. Recent measles outbreaks in the US and Europe have claimed dozens of lives already, and that number is only set to grow.
It’s also worth noting that the research is very good, and these really are the main risks from vaccines. Many people blame things like autism, Crohn’s disease, and autoimmune disorders on vaccines, but research has shown that this just isn’t true.
We know exactly what the main risks from vaccines are, and we can quantify that risk very well.
If you have questions about vaccines, the best place to go is to your doctor, or your child’s pediatrician. They can give you excellent advice on the risks and benefits for you and your child. The World Health Organization also has some great resources on their website.
Just remember: vaccines may have risks, but they have benefits as well.
Usually, the benefits far outweigh the risks.
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*Note: If you hate me for this pun, it’s probably no more than I hate myself
**Note: There are numerous common minor side-effects of the vaccine, as with most vaccinations, like redness and itchy skin, but we are going to ignore those. Many people get them, but they are gone within a day or two and rarely cause more than minor discomfort.
