Immunologists can work in a variety of fields, and they go by a number of titles. There are two roads you can take, which will make all the difference.
You can go the research route, which means you'll need a Ph.D. In this gig you will play with microscopes, develop drugs, and study disease…all in a quiet and sterile environment. This is great if you're not a "people person." You will also be earning some nice dough, somewhere between $80k-$100k. That will get you some sweet lab coats and possibly a girlfriend/boyfriend!
Your other option is to become a practicing physician, which means you’ll need your MD. Working as a pediatrician, general practitioner, or allergist is going to have you raking in $180k-$250k.
After a few years, who knows? You might snag a gig with a private company that makes vaccines. If that happens, you can triple your salary overnight. Say goodbye to college loans and car payments, y'all!