Did infectious diseases decline before vaccines were introduced?

“Vaccination does NOT account for the impressive declines in mortality seen in the first half of the century…Nearly 90% of the decline in infectious disease mortality among US children occurred before 1940, when few antibiotics or vaccines were available.” —

Annual Summary of Vital Statistics: Trends in the Health of Americans During the 20th Century,

Journal of American Academy of Pediatrics, December 2000

Here's a really interesting article on the subject:

https://www.learntherisk.org/diseases/