There was an autopsy of someone that got vaccinated and they found the spike protein in every organ. So if the immune system attacks them at one point, inflammation can always be the result. It doesn't have to be the case, but there certainly is a risk.

Given the low risk to young people (at least the data pretty clearly states this), I think it is irresponsible to get them vaccinated. Older people should get 15 boosters, maybe even for the rest of their lives or until better protections are available.