I had measles (and most other childhood diseases) before vaccines for them existed. Ever since, I have been blissfully confident that I had nothing more to worry about. Recently I read a theory (from only one source) that in the pre-vaccine era people were regularly exposed to these pathogens after their initial recovery, giving their antibodies a natural boost. Now that these diseases are rarely encountered, even naturally-acquired immunity fades over time. Can anyone comment?
