I managed to glean that he/ she is medically unfit for any form of military service and would like to know of any alternatives... Since you were keen on the Navy I'm guessing you're after something maritime related so the Merchant Navy might be an option depending on their health requirements. However I doubt any employer would be comfortable sending you around the world, potentially in charge of something very expensive, if you've not got all your jabs.
Alopecia is one thing, albeit merely a cosmetic problem, but if you could have your jabs without the supposed autoimmune reaction then you might have a shot - no pun intended.