I know hepatitis C only has been recognized in 1989 and hepatitis B has been known for a longer time. More information is known about hepatitis B so it easier to develop a vaccine when you have the rigth info.
Also hepatitis C is a RNA viruse and hepatitis b is a DNA viruse. Vaccine for RNA virus tend to be harder to develop du to high mutation frequency of RNA viruse. The influenza virus and HIV are RNA virus. There is a new vaccine for the flu every year (the vaccines are based on the projected mutation of the influenza virus) and there no working HIV vaccine yet .
Lack of info and that HCV is a RNA viruse migth explain why there no vaccine yet but I don't the actual reason.
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