Measles was no big deal when I had it. It was expected that everybody would get it. We didn’t go apesiht over it as illustrated in the episode.
Yes, I had it too. Like everybody.
Once a while, measles came to town and infected everybody, who have not had in before.
Then they disappeared, until there were just enough new, not yet immune, kids. I think, scientists could even estimate the frequency of those epidemics!
In the hypothetical case of Brady Bunch, the older kids would likely had it, before the younger ones were born. But yes, if somebody in the family got it, everybody else got it too, that was given!
Anyway, I do not remember being too sick. just got rash, some fewer and aches. Measles took longer than the usual colds and flu, like 10 days or 2 weeks??
The doctors were also pretty jovial about measles then. “Just something everybody needs to go thru”. Passage to adulthood.
I remember reading something like “in rare cases, serious complications can develop”, but I do not remember anybody getting any complications.
When they started coming up with the vaccine, I remember thinking - why bother?!