Mythconception: the flu jab gave me flu

25 January 2016

Interview with

Kat Arney, Naked Scientsits

This week Kat sticks the needle into a topic that's particularly contagious at this Needletime of year... the idea that the flu vaccine gives you flu. 

It's the season for coughs and colds, and while we might say we've caught the flu when we really just have a heavy cold or joke about the men in our life suffering from "manflu", the real thing - caused by the influenza virus - is deeply unpleasant and can be fatal for vulnerable people such as the elderly and those with certain health conditions.

Earlier this week I rolled up my sleeve for my annual flu jab, admittedly a couple of months late. As someone who suffers from asthma - and who also remembers the horror and subsequent months of hacking coughing due to having caught swine flu back in 2010 - it's as important a part of my winter routine as buying more pairs of thick black tights and remembering where I put the hot water bottle.

But just as with other vaccinations, there are several unfounded myths about the flu jab floating about, which might stop people who need it from taking up the vaccine. And one of the most common is the misguided idea that the flu jab gives you flu.

To explain why this is wrong, we need to take a step back and look at what's actually in a flu vaccine and how it works. Like many other vaccines, the adult flu jab is made up of inactivated flu viruses, designed to safely 'train' the immune system to recognise the infection and fight it off, should you encounter the real thing in your daily life. But while the immune system can recognise them and get ready to mount a response, there's no way these dead viruses can actually cause the illness itself. And even though the child flu vaccine - given as a nose spray - contains live flu viruses, these are weakened and also can't cause the disease.

So where did the myth that having the flu vaccine gives you flu come about? Again, like many other vaccines, having a flu jab can leave people feeling a bit rubbish - including having aching muscles, feeling tired and even getting a slight temperature. This is due to the immune system swinging into action to prepare itself, rather than flu itself.

And there's also a chance that someone who's just had a flu jab may catch flu by coincidence - or just get a nasty non-flu cold that the jab wouldn't protect them from anyway. It takes up to two weeks for full protection to kick in after a flu jab, but just a few days for a real flu infection to take hold - so if someone is infected just before or just after their shot, they're still going to get the flu. And the jab doesn't offer protection against all the strains of influenza virus that might be out and about in the wild in any given year.

So, while the flu vaccine isn't perfect, and it can't protect you against colds caused by non-flu viruses, it's still a life-saver for vulnerable people. And although my flu jab didn't give me flu, I did feel a bit off colour afterwards, so I went back to bed for the afternoon. That's my excuse, anyway, and I'm sticking to it!

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