Is it necessary to replace the timing belt when changing water pump on a Holden vectra?

There is no model called Holden Vectra. There is, however, a model called Vauxhall Vectra. Vauxhall does not have any models that use a timing belt. Instead, they all use timing chains. As a result, there is no need to replace a timing belt when replacing the water pump on a Vauxhall Vectra.