Can herpes zoster vaccine be given to an elderly with active zoster?

No: No, someone with active zoster will not benefit from the herpes zoster vaccine, which is used for prevention, not treatment.

Zoster vaccine usage: Zoster vaccine (Zostavax) has the greatest utility BEFORE someone gets the 'Shingles'. If a patient already has it - I would say it's 'too late' to give the vaccine. Perhaps a few years later, however, it might be worth giving it to prevent a subsequent attack. A natural infection with shingles is kind of like getting the vaccine - although u have to suffer with the disease! Better to vaccinate

Why ?????: Giving the vaccine to anyone with active shingles would be a waste of time, resources and effort. It would not treat the infection or benefit the recipient in any way.