Depends on what kind of sneezer you are. Are your post nasal passages all whack crazy backed up or reversed? Are you a phlegm cannon when you normally sneeze?
The gum would have germs on it, long before you sneezed. As soon as you put it in your mouth and chew, germs have attatched to it. A humans mouth is full of bacteria, no matter how much you brush your teeth and use mouth wash. Bacteria will still be there.
So whether you sneeze or not, your gum has already got bacteria on it, just from putting it in your mouth.