I seem to remember reading somewhere that most graphs you see about the effectiveness of vaccines show a sharp decline in the incidence of a particular disease just after the introduction of a vaccine BUT that if you can find the graphs that stretch out an earlier timeline, you'll see that the disease was already in decline presumably due to hygiene, quarantine, etc. and that after the vaccine, the disease continues to folllow a similar downward trajectory. I can't seem to find these graphs however. Does anyone know what I'm talking about or where I can find these?
Also, try a forum search. You'll probably find more types of graphs regarding this as well. This one was the first one I found.
Homeschooling mom to two boys '08 and '12