As far as the 'very
young and elderly', it says


the phrase you are looking for, and is used by food scientists, is:

"compromised immune system"

very young childred don't have much of an immune system and the elderly often
have lost much of theirs.

the point was that worrying about e. coli attacks from lettuce purchased in
foreign countries is worrying about a non-issue. anyone who does should never
untie their dock lines.