In New York [and poss. elsewhere], we need to track the number of certain immunizations that a student has received. e.g. it's not enough to say 'Johnny has a current DPT'. We need to say "Johnny has had four DPTs on these 4 dates, so he fulfills the requirement.'
Yes, our nurse assures me it is a legal requirement in our state to have the records include the several dates a student has had an immunization. There seem to be multiple requests for this type of enhancement (expiration dates, status, etc). I can't really even come up with a good workaround that doesn't involve having totally separate records for this :(