[sarasmom]

That was because people locally sought the mildest possible versions of those diseases to expose their children to, and garner future immunity, as safely and quickly as possible.
Particularly measles, for the future health of girls.

It was generally understood that exposing a pregnant woman without a measles immunity, was all but a death sentence for the health of a baby.
Nobody wanted that!

The vaccine was a natural progression for medicine, back then.
Get exposed to the lowest dose, as safely as possible, develop the immunity, and protect everyone was the goal.

BTW, chickenpox was the disease that protected people from smallpox.
That was the original, old-style “party” exposure, as I recall.
It wasn't until many years later that people knew that having chickenpox to avoid smallpox, meant that shingles was in your future....

[Roos_Girl]

It isn’t chicken pox that protected people from small pox. It is cow pox.