[CentOS] replace string with sed but not the first one

Tue Jun 19 05:30:11 UTC 2012
maverh at telenet.be <maverh at telenet.be>

We have a the following file 
# Unchanged IP addresses: 
# Please review default IP addresses mapping below: shared    -> shared 

We want to replace  to a other string but i don't want to change te first one.