Immunogenicity and safety of a live attenuated shingles (herpes zoster) vaccine (Zostavax®) in individuals aged ≥ 70 years: A randomized study of a single dose vs. two different two-dose schedules

Disease protection provided by herpes zoster (HZ) vaccination tends to reduce as age increases. This study was designed to ascertain whether a second dose of the HZ vaccine, Zostavax®, would increase varicella zoster virus (VZV)-specific immune response among individuals aged ≥ 70 y. Individuals aged ≥ 70 y were randomized to receive HZ vaccine in one of three schedules: a single dose (0.65 mL), two doses at 0 and 1 mo, or two doses at 0 and 3 mo. VZV antibody titers were measured at baseline, 4 weeks after each vaccine dose, and 12 mo after the last dose. In total, 759 participants (mean age 76.1 y) were randomized to receive vaccination. Antibody responses were similar after a single dose or two doses of HZ vaccine [post-dose 2/post-dose 1 geometric mean titer (GMT) ratios for the 1-mo or 3-mo schedules were 1.11, 95% confidence interval (CI) 1.02–1.22 and 0.78, 95% CI 0.73–0.85], respectively). The 12-mo post-dose 2/12-mo post-dose 1 GMT ratio was similar for the 1-mo schedule and for the 3-mo schedule...