Can I have "Vampires" as my research topic?

No subject is ridiculous - just depends on your handling of it. There are several approaches you can take on the subject - such as - a discussion on how they've been looked at in literature thruout history - they've gone from very feared satanistic monsters to almost teen idols in recent series - or you could look at popular culture imitators (I used to live across the street from a "vampire" bar in NYC - very interesting group of very young people).
It a fun subject and could be a very interesting read for your instructor if done well - you know they do appreciate things that are a little different.
As a teacher I like it when I'm thrown a well written and researched curve ball.

It sounds like it might be a tough one, especially if your instructor is expecting you to be serious. I have a feeling that you are going to find lots of misinformation that will be controversial (or, to put it another way, fake).

My favorite research topics were always horribly gruesome medical problems. Look up hemorrhagic viral diseases such as ebola, or things like fetus in fetu, or teratomas ("monster tumors" 'nuff said)... these are especially fun to do if you get to do a presentation on your topic and share the images in power point.

you should totally research vampires. i actually did a presentation on that topic once. it's so interesting and there's so much history on the different lengends. go for it!