>Is there some reason why we would expect a priori for the COVID-19 vaccine to have a particularly high risk of adverse affects that only show up long-term?

The correct question is, is there sufficient evidence that we shouldn't? You don't ever assume the confirmation of a hypothesis (in this case long term safety) when introducing something novel. That's the exact opposite of science.

My answer is: I believe in science, empirical evidence, and hypothesis testing. I'm not going to assume the hypothesis that they're safe long term is correct without empirical evidence. You don't disrupt baseline systems with something novel on the basis of faith when no empirical evidence exists. That's completely antithetical to science.

It's funny because most of your examples are great illustrations that assuming novel things are safe has disastrous consequences.