Dosing is a thing. There are high dose and low dose influenza vaccines for example. But even then immunity isn't guaranteed, you need neutralizing antibodies t

Dosing is a thing. There are high dose and low dose influenza vaccines for example. But even then immunity isn't guaranteed, you need neutralizing antibodies to develop as well. Lots of things have to go right to get a sustained safe and effective response which is why vaccines take so long to develop.