10 tricks of logic that underpin vaccine myths

The biggest lie those who create and spread misinformation perpetrate is that they want you to think for yourself. They warn their target audience not to be “sheep” and not to let themselves be told what to believe by “mainstream” voices, the “deep state” or other bogey men.

But in a classic case of misdirection, at the same time they warn you about this, they deploy a range of manipulative tricks to ensure you don’t actually think clearly or independently.

One of these tactics is to seduce you into subscribing to “logical fallacies”. These are flawed patterns of reasoning that sound convincing but lead to false or misleading conclusions.

Logical fallacies are like optical illusions of thought: convincing on the surface, but ultimately an apparition. Like a magician who tries to convince you he really has pulled a rabbit from a hat, getting you to fall for logical fallacies is a sleight of hand that aims to trick you into believing something is true that isn’t.

But when you know how a magic trick works, it no longer fools you. If you recognise the most common logical fallacies and understand how they work, they very quickly lose their power. Once you can see behind the curtain, the illusion fades, and you begin to understand things as they really are.

Here are ten of the most common ones you need to be on the lookout for when it comes to vaccine misinformation.

1. Appeal to nature fallacy

Typical claim:

Vaccines are unnatural, so they must be bad.

Fallacy: Assumes that natural is always better or safer, which is not logically or scientifically valid. Plenty of natural substances are very harmful or deadly, and plenty of man-made products, including many medicines, are life-saving.

2. Slippery slope fallacy

Typical claim:

If we allow vaccine mandates, next we’ll lose all medical freedom.

Fallacy: Assumes a minor or reasonable action will inevitably spiral into something more extreme and implausible. This is one of the easiest logical fallacies to spot and relies on stretching logic to its breaking point in order to provoke fear. Politicians particularly like this tactic.

3. Ad hominem fallacy

Typical claim:

You can’t trust that doctor, he’s obese and doesn’t know how to look after himself.

Fallacy: Attacks the person instead of engaging with their argument or evidence. This is usually the go-to strategy when one either has no evidence to back up what they are saying or doesn’t have any capacity to engage with the evidence.

4. False dichotomy fallacy

Typical claim:

You either trust vaccines blindly or you’re a free thinker.

Fallacy: Ignores the nuanced middle ground and oversimplifies the choices. Often this is a version of the “you’re either with us or against us” ploy. It frames the debate so that one option is clearly unreasonable, creating the false impression that the right choice is obvious.

5. Straw man fallacy

Typical claim:

Pro-vaccine people think vaccines are perfect and have no risks.

Fallacy: This may be the most relied upon tactic by those spreading vaccine misinformation. It relies on misrepresenting the evidence to make it easier to attack. It often involves a number of different tactics such as distorting, cherry picking or oversimplifying the evidence. RFK Jr is a big fan of this tactic.

6. Post hoc fallacy (false cause)

Typical claim:

My child got sick after a vaccine, so the vaccine caused it.

Fallacy: Confuses correlation with causation without considering other explanations. Just because two events occur at about the same time doesn’t mean one caused the other. The false belief that the MMR vaccine causes autism stems from a single fraudulent study that wrongly inferred causation from a mere correlation.

Read more: If 'correlation doesn’t imply causation', how do scientists figure out why things happen?

7. Bandwagon fallacy (appeal to popularity)

Typical claim:

Millions of people are questioning vaccines so there must be something wrong.

Fallacy: Assumes that a widespread belief is equivalent to truth. This is also called the “illusory truth effect” and it’s one of the main reasons misinformation has such an influence on social media. When people find themselves in echo chambers where they are led to believe a view is commonly held, even when it is obviously untrue, they are more likely to believe it. Humans are wired up to follow the herd.

8. Anecdotal fallacy

Typical claim:

I know someone who got vaccinated and still got sick so vaccines can’t work.

Fallacy: Uses personal stories instead of statistical or scientific evidence. This is equivalent to the reference to the grandmother who smoked a pack of cigarettes a day and lived to be 100 years old. It’s often the go-to strategy when there is no evidence to support a claim. Apart from the fact these anecdotes are usually not verifiable, anecdotes are no substitute for rigorous scientific evidence.

9. Perfectionist fallacy

Typical claim:

Vaccines aren’t 100% safe and effective, so they are useless.

Fallacy: Rejects a good solution (vaccines) because it is not perfect. No medical intervention is 100% risk-free. Even something universally used like aspirin can have side effects, and so an extension of this logic is that every single therapeutic intervention is useless because it is not perfect, which is absurd.

10. Base rate fallacy

Typical claim:

More vaccinated people are getting sick, so vaccines don’t work.

Fallacy: In a highly vaccinated population, most people will be vaccinated and inevitably some vaccinated people will still get sick. While the absolute numbers of vaccinated people who get sick will outnumber those who did not get vaccinated and got sick, this is misleading as the proportion will be much smaller due to the sheer numbers of vaccinated individuals in the population.

In a nutshell

We live in a time where bad-faith actors are easily able to spread deliberate misinformation. Therefore, we all need to educate ourselves in the tactics and tricks used by these con artists, so we’re not fooled.

Being able to recognise how logical fallacies are used to make misleading arguments seem persuasive is one of the things we can do to protect ourselves. The good news is, once you understand the most commonly used logical fallacies, it’s harder be to fooled.