Well, the stats on life expectancy over time, cases of infectious diseases and analysis of vaccination programme efficacy are acceptable evidence. You don't ne

Well, the stats on life expectancy over time, cases of infectious diseases and analysis of vaccination programme efficacy are acceptable evidence. You don't need to understand the mechanism of vaccines, to see data of the effects. Luckily the effective application of science frequently allows us to see that the consensus did in fact improve something, and that even if it's not 100% correct or you don't understand all the nuance, the fact that repeatable and extensive datasets are available for many scientific claims will work in its place. Of course there are huge exceptions to this, but it's not always true that you need to understand to have an opinion else it is simply faith. It can be knowable and verifiably effective. You don't need to understand combustion engines to know that they transfer energy. You don't need to trust that scientists made them more efficient when you can measure distance travelled and volume of fuel required.