I don't think many, if anyone, here are suggesting that vaccines are 100% safe all the time.
What they're suggesting is that at the very least there should be EVIDENCE of a possible danger if you're going to act like that danger exists.
If someone decided they didn't want to vaccinate their kid for MMR because they have a roughly a 0.000001% chance of having a severe reaction to it...fine. I'd think that's rather stupid, but at least they're going off something with some legitimate evidence backing it.
That's not what people are complaining about primarily. What they're complaining about are people not doing it because they think it'll cause their kid to have ADHD or Autism, something with no credible evidence suggesting it occurs what so ever.
There is as much credible evidence saying that drinking H20 causes autism or ADHD as there is saying that vaccines cause it. If your only argument against vaccines is that "they haven't proved 100% that it doesn't" cause ADHD or Autism then you better stop them from drinking water as well, becuase using the same standard they haven't 100% prove that water doesn't cause those issues either.