If it was known that those products had a high chance to be contaminated, no amount of consent would make any of this ethical. The only ethical way to use them would be if there was no alternative available and the potential infection with Hepatitis C or other viruses would be less dangerous than no treatment at all.
Consent is a necessary requirement for an ethical clinical trial. But it is not sufficient by far, the risks and benefit of the trial need to be proportionate for the patients.