why does hep c use its own RNA-P

So, Ive been reading that there has been no vaccine for Hep C because of antigenic variability due to lack of 3-5 proofreading activity in virion encoded RNAP . MY question is, HepC being a +sense RNA flavivirus, doesn't it use HOST RNA-P?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums