Why Some People Get Sick From the Flu Shot

Cliche but mandatory disclaimer that I’m not a doctor.

It seems that there are two main thinking camps when it comes to the flu shot.

Either you believe that the flu shot absolutely causes the flu and you should never take it, or…
You believe it’s actually impossible to get the flu from the flu shot, and that anyone who disagrees probably also thinks the flat earth climate changed on 9/11.

As it turns out, the truth is more nuanced but still very simple.

Keep in mind that one doctor does not make data.

I already mentioned I’m not a medical professional, but I just asked my doctor today about what I’m about to tell you, and he 100% agreed. You should do the same with your doctor.

Anyway, it all comes down to a few points:

The flu shot doesn’t contain live virus so it’s not capable of actually giving you the flu.
The shot works by stimulating the immune system, so when someone gets it there’s an immune response that can actually make you feel sick for a bit—unrelated to the actual flu.
Just because of the numbers at play, there are also times when people were already about to get the flu—or already had it and didn’t yet have the symptoms—and then they get the flu shot and come down with it shortly after.

Think about those three things, and how they combine in situations where hundreds of thousands of people are getting sick, getting the vaccine, and getting the flu.

Given those numbers, there’s simply no question that many, many people have gotten the flu right after getting the vaccine. Period. It’s just a matter of probability and coincidence.

Think about it:

Tons of people at any moment are about to get the flu, and there’s nothing that can be done to stop it.
Some percentage of those people are also going to get the shot right before they start showing symptoms.
Therefore, many people will get the flu right after they get the shot.

Does that mean the shot caused the flu? No.

Plus, there’s a whole other set of people who feel like crap, i.e., sick, for a day or so after getting the shot—purely because it’s a kick in the shins to your immune system.

Some of those people get the flu right after (because they were already going to get it anyway), and some get better immediately and develop the resistance to flu.

Ok, so…where does that leave us?

The flu shot can’t directly give you flu because it doesn’t use live virus.
The shot can make you feel bad, however, because your immune system is under temporary load after you get it.
Some people who take the flu shot were about to get it anyway, and since it takes a couple weeks for immunity to build up, there was no time for the shot to protect you.

This simple set of three facts explains pretty much every situation I’ve heard being debated on social media about the flu vaccine.

It explains people who’ve felt bad afterwards (including me), it includes the people who’ve gotten the flu right after taking it (surely quite a few), and explains the data showing the shot absolutely helps overall.

It also explains all these things in a way that acknowledges people who’ve actually gotten sick from shot, or even gotten the flu after it, rather than dismissing them as crazy.

Remember, people do actually die from wearing seatbelts sometimes. But that fact does not counter the data on the benefits of seatbelts.

Summary

So, my advice (as your non-doctor) is very simple:

Get a flu shot. Seriously.
Try to get it when you’re healthy in order to avoid additional load to your immune system.

It’s that simple.

Don’t wait until everyone around you has the flu and you’re starting to feel bad.

Because if you do, you might actually get the flu right after—because you were going to anyway—and then you’ll be another person the internet talking about how the flu shot gave you the flu.

Don’t be that person.

Notes


I saw a funny joke about this topic on Reddit the other day. Someone said they got the flu from the flu shot and a commenter said, “Well sounds like you got the flu shot instead of the flu vaccine shot!”. That was funny.
I’ve gotten sick from a flu shot a couple of times, but I’ve never gotten the flu from it. It was just a couple of days of blah—-as if someone kicked my immune system in the solar plexus.
This piece here is an exercise in logic, and I encourage you to take it to as many doctor friends you can find. I’m curious what they think of it. I’ve only asked a few, but they said this was fully in agreement with both their training and their experience in the field.

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