Most early vaccines were less dangerous viruses related to more dangerous ones and which provided cross-immunity once free immune system had learned it.

Then there’s been plenty of vaccines with dead virus particles, as well as modified live viruses (dangerous viruses which was weakened, neutralized, or sterilized, or even mild viruses equipped with recognizable but harmless proteins from dangerous viruses) to more safely expose you directly to the pathogen.

Then mRNA and protein subunits and some other types drops the full virus part and provides methods to expose you to only small pieces