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  • Alex Cloherty

What's up with the flu vaccine?

Updated: Aug 26, 2020

At work, at school, at home, you hear it."Why would I get the flu vaccine? I don't trust it. I got it two years ago, and it was the first year in ages that I caught the flu!" I hear statements like this pretty often, and I would guess that you also do. So why is it that the flu vaccine doesn't seem to work as well, or as consistently, as the ones against diseases like hepatitis or measles?

The reason is that the influenza virus, which causes the flu, is a costume artist.

Take a moment and think back to your childhood bedroom. If you were anything like me, you had a big RubberMaid box in one corner of the room filled with costumes. Costumes from past Halloweens, handed down from older cousins, some elaborate self-made varieties... Lots of costumes. Well, the flu virus is an artistic and spoiled child. It can change how it looks to just about a gazillion different costumes. Remember the Faceless Men from Game of Thrones? They've got nothing in terms of costume-changing compared the flu virus.

These constant costume changes of the flu virus makes it really hard for our immune system to recognize. The immune system will think something like, "Ok, last year the flu was about 5'8'', blonde hair, brown eyes, wearing a green dress with polka dotted tights. It probably looks the same now, so that's what I'll keep an eye out for." Oh, poor, naive immune system. It doesn't realize that since last year's infection, the virus has swapped clothes... And hair... And eyes... You get the idea.

The same problem occurs when you are vaccinated against the flu. When preparing the flu vaccines for the coming year, researchers use an elaborate mix of math and biology to put together a 'Wanted' poster for this year's virus. They are able to predict with some accuracy what costumes the virus is most likely to be wearing. When they get it right, a vaccination acts like a briefing of your immune system. When you get that shot, you're effectively showing your immune system a wanted poster. Sometimes, it's right, and you won't get the flu! But, sometimes, the virus makes such an insane costume change that even our best, smartest scientists couldn't have guessed it would go for a green plaid kilt with silver, sparkling, knee-high, high-heeled boots and a striped turtleneck sweater.

This actually starts to explain why sometimes, it is indeed that one year that you got the flu vaccine when you also get the flu. Most years, the flu virus doesn't make a complete costume change. For instance, if last year, the flu had blue eyes and blonde hair and was wearing a cow onesie, this year it may have switched to business-casual clothes but still have blue eyes and blonde hair. If your immune system paid more attention to the eyes and hair than the cow onesie last year, you'll likely still be protected this year! Same goes for the vaccine - it likely protects against flu with blue eyes, blonde hair, and/or cow onesies. But occasionally, in the years where the flu hits humans the worst (think the 1918 Spanish Influenza, or the 2009 Swine Flu Pandemic), the flu has gone all out and completely changed. In these years, you may not be protected by either your immune system or the virus: because the costume change was completely unpredictable.

So, that brings us back to the question inherent through all of this. Does it make sense to get the flu vaccine? Personally, I do get it. I think of the problem like this: looking both ways before you cross the street doesn't 100% eliminate your chance of getting hit by a car. But it sure helps. Same thing with the flu vaccine: it may not 100% guarantee that you won't get the flu, but it doesn't hurt. Not more than a pinch, anyways.

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