Vivian Patrick Campbell (born in August 25, 1962 in Belfast, County Antrim, Northern Ireland) is a Northern Irish rock guitarist and a member of Def Leppard. Prior to joining the band in April 1992, he had been a member of the Irish rock band Sweet Savage, Dio (October 1982-March 1986), Trinity, Whitesnake (April 1987-late 1988), Riverdogs, and Shadow King.
from wikipedia: Campbell is also a Vegetarian like three of his Bandmates. [we only know of two others]
from Vegetarian Times Magazine (March 1993), article on Phil Collen:
He hasn't had to coax his band members to accept his choice. In fact, drummer Rick Allen and guitarist Vivian Campbell have become vegetarian on the strength of Collen's example, and even the not-yet-veg band members are becoming more aware of what they eat and the world around them.
from msn.com - interview with Joe Elliot, Def Leppard singer, May 2006:
We have two-and-a-half vegetarians in the band.
This appears to be referring to Vivian Campbell as a pescetarian (fish-eater) whilst Phil Collen and Rick Allen are vegan. Many website simply list all three of them a 'vegetarian'.