Background Efficacy of the adjuvanted recombinant zoster vaccine (RZV) against herpes zoster (HZ) was demonstrated in pivotal trials ZOE-50 (NCT01165177) and ZOE-70 (NCT01165229). This study was designed to offer RZV to placebo recipients of these parent studies. Methods Vaccine safety and suspected HZ episode occurrence were assessed for 12 months following vaccination. Results Of the 14,550 eligible participants, 8687 received RZV and 97.8% completed the 2-dose schedule. During the 30-day post-vaccination period, 5175 (59.6%) participants experienced ≥ 1 unsolicited adverse event (AE), 4422 (50.9%) were vaccination-related. The most common AEs were injection-site reactions, pyrexia, and headache. During the study, 734 (8.4%) participants reported ≥ 1 serious AE (SAE) and 62 (0.7%) reported ≥ 1 potential immune-mediated disease (pIMD); 2 of each were assessed as vaccination-related. Suspected HZ episodes were reported by 30 participants (0.3%). Conclusions Nature and incidence of AEs, SAEs, and pIMDs were as expected and in line with the parent studies.