Why Are Flu Jabs Painful?

I’ve just had my annual flu shot, and my arm hurts like a son of a bitch. Now, I’ve had plenty of injections in my time, but it’s only the flu shot that makes my arm hurt like this. Friends of mine who also have the shot tell me the same thing. So yeah, why is the flu shot so painful?


You may just have a vigorous immune response to the vaccine. Anecdotally, my responses have always been quite mild; to the point that if my arm aches slightly the next day, I have to think back to think why that might be. So apparently, it’s a somewhat idiosyncratic thing.

Indeed and it will not just vary by individual, but at times from year to year as well. Not so surprising I suppose, since the makeup of the vaccine changes every year as well. I had a strong soreness reaction exactly one year - my arm felt like it was on fire the next day. Every other year? Very slight soreness to nothing. This year there was absolutely no reaction at all.

No, I wouldn’t say the flu is the only vaccination that hurts or causes a sore arm. Most of them do. When was your last tetanus booster? Flu is probably the only vaccination you get year after year.

I had zero reaction to mine - I never do. The last reactions I remember to vaccines was over 50 years ago when I got a ton before going to Africa. Some people must react to shots more than others.

I have never had a reaction of any kind until this year. My arm hurt like hell and I felt like crap for a day and a half. Still better than the flu.

Flu shots typically only give me a mild sore spot for a couple of days.

That damned dip/tet booster thing they gave me when my wife was pregnant made my entire deltoid area on my arm turn red, hot and firm for nearly a month. Dr. was like “Huh. It’ll go away eventually.” And it did, after another couple of weeks.

Yeah, my last tetanus shot gave me a sore arm for a couple days, but it was pretty minor. I viewed it as a good thing - I actually had a vaccination and my system was reacting/taking notes to so as protect me in the future.

Isn’t “sore arm the next day” the most common side-effect of getting a vaccination?

It’s the tensing up before the injection into the deltoid muscle.

I get B-12 shots. Monthly. Subcutaneous. I could just stand, loosen my pants and get one in the upper hip. Could hardly feel it.

The last shot, a different nurse had me bend over tightening my gluts (that’s what the nurse wanted). That stung, and hurt after. And from what I’ve been reading has no better effect than sub-c.

I don’t buy this. I’m completely relaxed when I get inoculations. Twenty plus years in the military makes you pretty much blase about injections of any sort. But the flu shot still makes my arm sore, while others don’t.

I got vaccinated yesterday, I feel nothing, unless I press the spot where the injection took place. Like every other time, in fact. I never had any kind of reaction or significant soreness from a flu vaccine. So, I guess it just depends on people.

It depends, not insignificantly, on the person administering the shot, in particular how good their aim is.

Hmm. I had my flu shot a few weeks ago and I don’t recall feeling anything at all-- I barely felt the initial jab, and don’t remember any soreness the next day. Different people, different reactions. shrugs

I suppose that in a given year everyone gets the same vaccine brew? Not sure…Maybe you’re just sensitive.

Perhaps “jab” is the problem. I got my flu shot from a nurse that is excellent at inserting needles, barely felt it, and had no reaction.

I was whining to my friend about my sore arm the other day. She told me that this year was the only one where she didn’t have a reaction.

Most years, yes, the flu shot hurts. This year it didn’t.

On the other hand, the injection site always itches for a day or two afterwards. I don’t know why this is.

This year, for the first time ever, I had quite a reaction – it hurt like crazy a couple of days later.

It felt like I had sprained a muscle in my shoulder, and hurt the joint, and hurt whenever I raised that arm above chest high. But I couldn’t remember pulling a muscle there. I actually talked to a nurse, who eventually pointed out that I had got a flu shot in that shoulder 2 days before, and that was probably the cause. Said it was a common reaction this year. Apparently so, because it began fading the next day and was gone 2 days later. But a surprise to me, since I’ve never had anything but a bit of swelling & minor itch at the injection site.

My immune system is best described as “aggressive bordering on opportunistic seek and destroy”. The flu shot this year laid me out. My upper arm turned a bright read and became hot to the touch, I ran a high fever for a day and felt really, really ill. It took almost a week before my arm didn’t feel like that anymore.

In the other arm, DTaP and Gardasil - no reaction.