Vinny From 'Jersey Shore' -- Grilled ... How Many STD's Do You Have?

Vinny from "Jersey Shore" was the latest victim of a college prank -- when a student hilariously interrupted a speech he was giving, to ask him a very important question ... specifically how many STD's he got from being on "Jersey Shore?"

Vinny -- who is on a college speaking tour right now to teach others how to overcome anxiety -- was at Niagara County Community College Wednesday ... when he was caught off guard by a prankster planted in the audience.

In the video ... a student uses the very serious Q & A session to ask Vinny a not so serious Q ... mainly, whether or not he contracted any gross diseases from "Shore" -- ya know because of all their sexual shenanigans.

Vinny, in an ironic twist, gets pretty anxious about the whole thing -- and then shoots off some choice words to his new friend.