Acyclovir, Adolescent, Adult, Aged, Aged, 80 and over, Child, Cost-Benefit Analysis, Double-Blind Method, Female, Hepatitis, Viral, Human, Herpes Zoster, Humans, Immunocompromised Host, Infusions, Intravenous, Male, Meningoencephalitis, Middle Aged, Neuritis, Pneumonia, Viral, Skin Diseases, Infectious, Vidarabine