The invention provides consensus sequences for hepatitis C virus 1a and 1b. Also provided are non-synonymous changes for each residue of the consensus sequences. These sequences are useful as compositions or vaccines for prophylactic use or treating HCV-infected individuals. Also provided are methods for lessening the chances for a HCV-infected individual to enter a chronic phase of infection and methods of diagnosing an individual with HCV 1a or HCV 1b infection.