Jesserry

let's check here....did you ever have a medical exam by an authorized licensed doctor , not only vaccination documents?
If so they should have filled out this form I-693 for you and as Shescott responded given a copy to you.
Normally you should have submitted it along with your AOS package, if you didn't, there's a chance you will get a "Request for Evidence (RFE)" and/or you will just bring it along on your interview date.
As far as your question regarding SEALED goes - the form filled out by the doctor is put in an envelope which is glued closed, in most cases having additional stickers on it so it's clearly visible if you would have opened it. But you MUST NOT open it or USCIS will request a new one, plus you really should get a copy from the doctor's office for your records of it.
Hope this is understandable, if not, ask and I'll try to explain it otherways
Maxximus
edit: just re-read your post and I see that you are quoting your letter for the interview - it looks like to me that you didn't submit the form I-693 with your AOS - so you need to make an appointment as soon as possible as you will need the "results" to be handed to the officer giving you the interview. Keep in mind that they will need to do a TB skin test which requires you to go back to the office in 3 days to have the results from it. There is also a chance that they need to do a chest x-ray for that and that may take even longer......
Good luck for the interview!!!