The nice thing about the mRNA vaccines is that while that tech hasn't been used in an approved vaccine before, it has been used in other treatments, and there's

The nice thing about the mRNA vaccines is that while that tech hasn't been used in an approved vaccine before, it has been used in other treatments, and there's no real mechanism for there to be long term side effects. The vaccine and the proteins it causes to be produced are only in your system for a limited time period. Long term side effects are more of a concern for medications that are taken on an ongoing basis. Currently if I had the choice I'd go for the Pfizer vaccine hands down, given the superior efficacy in testing. (That said, beggars can't be choosers, so I'd take any approved vaccine I could get...)