In the absence of evidence, it seems logical to me to use the closest analogues we have to make predictions while not being beholden to them. Historically, injections to prevent diseases have manifested the bad reaction quickly after the injection (allergic reaction, and so forth). I am not aware of any vaccines that years later caused adverse reactions, although I'll readily admit I haven't looked exhaustively into the matter. Therefore, to me, it seems fair if you're making predictions based on the evidence available--which is really all anyone can do at this point--that you would say "it's probably more likely reactions will happen in the short term and not the long term." Granted there may be low confidence in this assertion.
Again, I'm just curious how the people who are so sure this is going to eradicate all humans in [x] years have arrived at that conclusion. Once more for the record, I have some reservations about the vaccine, and certainly would not advocate for it being mandatory or whatnot, but I would just like something--anything--from the people who keep repeating that this is going to kill everyone on how they arrived at that conclusion, other than a general "I don't trust the gov't and big pharma." I don't trust them either, but I was kind of hoping there was some more meat to the claims, something like "well vaccine [x] acts on protein [xyz], and in lab studies it's been shown to take three years to demonstrate [abc], so we'll need to wait until then to see this..."
Instead, I get zombie/women growing penis memes that, while they sometimes make me chuckle sometimes, are not persuasive. I am open-minded and willing to look at things, I just haven't seen anything yet.