Comparison of a Live Herpes Zoster Vaccine and a Recombinant Vaccine in 50-59 and 70-85 Year Olds

This study will compare the two vaccines that have been developed to prevent and/or lessen the effects of shingles. One vaccine is live (Zostavax, licensed by FDA) and the other, herpes zoster subunit (HZ/su), contains a piece of the shingles virus (not live) and an ingredient that may enhance the body\'s immune response to the vaccine, and is currently investigational. The vaccines are being compared to assess their ability to stimulated protection against shingles. The study will provide an opportunity to determine the safety profile of each vaccine in a single trial. The study will also look at the effect of age on the immune response to the two vaccines and on the persistence of these responses.