You obviously haven't, though to be fair no one actually bothers.. everyone just believes the myths touted by the education system as fact. If you had, you would discover that for the major disease epidemic/pandemics of the 19th/20th century for which deaths were recorded, there was a massive decline in mortality before their respective vaccines were introduced. In the case of Measles, 95-99% drop in mortality before the vaccine was introduced.
The point being, vaccines had absolutely nothing to do with the decreasing mortality of the major diseases. In the case of Scarlet Fever, which was one of the most feared and biggest killers (it had a global pandemic in the 19th century), no mass vaccination even took place.. it simply decreased without our medical intervention.
What did cause the mortality to drop was: increased water quality, increased food quality, increased sanitation provision, increased living quarters standards. Most people have no fucking idea what life was like, even up until the early 20th century. When you live an extreme stress lifestyle (working 12 hour days, work houses, slum living, etc), with poor nutrition/water/sanitation, your body can no longer do what it is supposed to do and it begins to break down. If you reverse those conditions, then the body is quite capable of maintaining a healthy equilibrium on its own.
We created those epidemics and pandemics out of our own ignorance, and with a little help from the ruling class who forced people into dense slum cities to work in factories during the industrial revolution.