I have heard reports of people having long covid-like symptoms from the vaccine and needing treatment. That may not be significant to some folks, but to others it might well be. I'm not saying that their evaluation is correct, BTW, but I think it's difficult to make the argument that the vaccine is 100.0000% upside.

Even if the rate of people having these long covid-like symptoms is lower than that of people who get covid it's still not riskless even though the risks are lower.