Because of the anti-vax movement, it's impossible to debate this rationnaly. The antivaxers will not listen to any argument. But the others also accept anything "vaccine" without thinking like steve irwin or mr roger: it's good, and you can't say anything bad about it.
But again, in medecine, there is no such things as a free lunch. Any drug has known and unkwown side effects, and interractions with the env, and should be use if it's worth it. It's then important to debate what is.
This is simply false.
We've got millions of people in an experimental group - those who regularly get their flu shots. We've got millions in a control - those who don't.
If the flu shot were impacting health negatively, we'd know by now. The first flu shots were given as far back as WWII.
The general populatuon is not a control group.
Someone else in the comments mentions that last years vaccine was particularly ineffective, at only about 50%. Google says the vaccine costs ~$40, so since it's only 50% effective, let's double that cost to $80 to account for the odd year where it isn't effective¹. (And that's a bad year, so typically, we can expect better.) So, what's cheaper: spending a week in bed miserable, trying to get over the flu and the lost productivity entailed by that disease, or $80? My time is definitely worth way more than $80 — even at minimum wage it's likely a payoff, if not just that I think most of us would willingly just pay that $80 to avoid the misery. (I mean, I do: I get the shot. It's also covered for me by my healthcare, so it's sort-of $0 to me, personally. I don't get $80 back if I don't get it.)
¹I'm not sure if this is quite the statistically right way to do this, but I think it's close enough that the point holds. My point is that, even conservatively, getting the vaccine pays off.
That it might save you a couple of days of misery is a nice bonus, but not the primary reason to get the shot.