The publisher has decided to shift the Radical-developed title's release because it ‘needs more time to deliver the game the team initially set out to create'.
Sierra showed off the game at its Spring Break event in Mallorca last month.
Sierra told MCV in a statement:
‘Sierra Entertainment and Radical Entertainment have made the decision to shift Protoype to launch in 2009.
‘Since its announcement, Prototype has been regarded by many as groundbreaking and taking the open-world genre in new directions, and in the simplest explanation possible, we need more time to deliver the game the team initially set out to create.
‘Both Sierra and Radical are fully aware and appreciative of the multiple ‘Most Anticipated Games of 2008' accolades and continued enthusiasm by all, however, date changes are common in this industry, especially for publishers and developers committed to launching great games. Further details on Prototype's 2009 launch timing will be revealed at a later date.'