The invention concerns a pharmaceutical composition for treating or preventing C hepatitis (HCV), induced infections, which in a preferred embodiment, comprises a main active principle, (i) a fusion polypeptide, including the HCV capsid polypeptide (C191) and polypeptide coat (E1) and in which at least one cleavage site 173/174 and 191/192 has been made inoperative by mutation; (ii) an equimolar mixture of the C191 polypeptide of which the cleavage site 173/174 has been made inoperative and of the E1 polypeptide (mixture equivalent to the fusion polypeptide); or (iii) a DNA molecule coding for this fusion polypeptide. Products (i) to (iii) are characterized in that the C191 element is incapable of regulating the functioning of the genes, in particular of causing them to interact. Such a composition can also include any form equivalent to the products described above.