How does a person who has been told he is clear of hepb if he can resume having sex? can he ever not infect someone not vaccinated for it during sex?

Yes, resume sex: If you have been told that you are clear of hepatitis b, that means that you are not making the virus in your blood and cannot pass it on. After infection, a very small amount of virus lays dormant and only under very unusual circumstances can it be reactivated. Check to make sure that you understood your doctor, but otherwise you should not infect your partner.

Hepatitis B: If you have cleared hepatitis b, like many do, then you are no longer contagious and cannot infect another person.