Safety, tolerability, and immunogenicity after 1 and 2 doses of zoster vaccine in healthy adults ≥60 years of age

► One dose of zoster vaccine (ZV) elicits substantial protection against HZ. ► This study examined impact of a second dose of ZV. ► ZV was generally well-tolerated and immunogenic in adults ≥60 years old. ► 2nd dose of ZV was generally safe, but did not boost VZV-specific immunity beyond postdose 1 levels.