I remember that being a plot point in Asimov stories: people from earth are eventually treated as inferior because they are potential carriers of sicknesses tha

I remember that being a plot point in Asimov stories: people from earth are eventually treated as inferior because they are potential carriers of sicknesses that don't exist anymore in colonised planets, and for which the habitants no longer have natural defences. That, combined with the new planets' ability to form new societal structures (unlike Earth that has to work with the legacy existing ones), end up leaving earth as a backwards, shunned place.