No medicine, no vaccine is 100 percent safe. It is a question of which is worse, get protection from a virus that is know to kill x percentage, or vaccinate everyone with the risk of dying from that vaccine with y percentage.
As long as y is significantly less than x, it is a good idea to vaccinate everyone.
It gets grey with vaccines preventing transmission as was originally thought, it only seems to reduce transmission somewhat.
The question is; should you vaccinate perfectly healthy younger people to protect the older or weaker population, thereby exposing the healthier people to a higher risk of death from just the vaccine, where they had a very low chance of dying from Covid to begin with.
Is the reduction of transmission enough to warrant a higher risk for the healthy population?
One day we will know, and it will be too late to change anything.