I've never met a scientist who said anything is 100% fool proof. I'm sure there are, and that's unfortunately.

But, in order to make sense of this universe, we have to have some sort of standard for quality when it comes to science. And one of the few ways we can ensure that is massive amounts of data. The more data, from more fields, from more labs, with more variables, etc. only help to filter out bias, fraud and mistakes and eventually help us reach a conclusion that is as close to the truth as possible.

At the present, the meta analysis of all research on vaccines and its link to various diseases is negative. Any outlier results that point away from the concensus get absorbed into and weighed against all the other evidence equally. And in the end, where the scale tips is the only rational place to form a judgement.

Sometimes that scale is more even, sometimes it is heavily weighted to one side. In the case of vaccines, the "no-association-with-autism, etc." side of the scale is basically bolted to the ground. The only real way to invoke healthy skepticism is to cite a small probability for massive error. Which is still possible, but that's not the argument I ever hear surrounding skepticism and vaccines. It's usually "but look at this evidence over hear saying their is a link". Or "what about the FDA and corruption, etc." Which have little meaning, considering any of these arguments can be weighted against evidence that cancel out these arguments. For example, there is tons of evidence done around the world that have nothing to do with the FDA, or the U.S., or big phama that still show the same results without those factors.