bk613: “There is also no proof that learning gemorah doesn’t cause heart attaks.”
I don’t think that’s an accurate comparison. Maybe there is an increased risk of heart attacks if someone learns Gemara. But it doesn’t matter, because we have a chiyuv to learn Gemara whether or not it is physically healthy to do so. (I’m not talking about a case where it is known that someone will drop dead the second he starts learning).
On the other hand, the whole purpose of vaccinations is to help one’s physical health. It is an act of hishtadlus and one has to make sure it is reasonable hishtadlus. The benefits are only possibilities and the risks are only possibilities. One has to weigh the likelihood of each against each other. And if nothing has been proven one way or another, I would think that it might make sense to assume that there could be some potential risks involved in any medical procedure.
Again, I am not saying one should or shouldn’t have vaccinations. I am simply discussing the logic of the arguments being used.