Dripping hand held shower head in off position
The vacuum breaker is there to prevent dirty water from contaminating the fresh water supply in the (unlikely) event you were to drop the hand-held unit into standing water at the bottom of your shower enclosure while at the same time there was a drop in city supply pressure (like due to a fire engine pulling from a hydrant on your street). Your equipment will function perfectly fine without one.

Any leak/drip from anywhere downstream from the control valve(s) would mean the the valve(s) need servicing (not necessarily replacement). If you post a new question with pictures of the handle(s)/knob(s) we might be able to help you fix it.