Immunogenicity, Safety, and Tolerability of Live Attenuated VaricellaZoster Virus Vaccine (ZOSTAVAX™) in Healthy Adults in India

Abstract

Background: Herpes zoster (HZ) is caused by varicella-zoster virus ( VZV ) reactivation. In the United States, Zoster vaccine (ZOSTAVAX) is indicated for HZ prevention in patients ≥50 years.

Aims: To evaluate the immunogenicity, safety, and tolerability of ZOSTAVAX in healthy Indian subjects, to support its registration in India.

Methods: This open-label, single-arm study was conducted at 10 sites in India. Healthy Indians (≥50 years) received a single ZOSTAVAX dose. Immunogenicity was assessed by VZV-specific antibody titer using gpELISA assay. VZV-specific antibody geometric mean titers (GMT; Day 1 pre-vaccination, Week 6 post-vaccination) and geometric mean fold-rise (GMFR; Week 6 post-vaccination) were assessed. Safety was evaluated by the incidence of adverse events (AEs) and serious adverse events (SAEs) within 42 days of vaccination. Two-sided 95% confidence intervals (CIs) were evaluated using t-distribution with natural log-transformed values.

Results: Of the 250 subjects (mean age, 58.6 years) enrolled and vaccinated, 244 subjects completed the 6-week follow-up. Overall, subjects in the per-protocol population had GMT of 149.8 gpELISA units/mL (n=250; 95% CI: 132.6, 169.2) at Day 1 pre-vaccination, and 410.8 gpELISA units/mL (n=243; 95% CI: 373.0, 452.6) at Week 6 post-vaccination. GMFR of VZV-specific antibody from Day 1 pre-vaccination to Week 6 post-vaccination was 2.8 (95% CI: 2.5, 3.1). Overall, 67 subjects (26.8%) experienced AEs, with 48 (19.2%) reporting injection-site AEs and 38 (15.2%) reporting non-injection-site AEs. SAE-abdominal pain and bronchitis-was reported in one (0.4%) patient each. There was one death, which was unrelated to the vaccine.

Limitations: Since ZOSTAVAX introduces a new live attenuated virus, clinical reactivation of ZOSTAVAX virus and wild-type VZV will need to be differentiated.

Conclusions: In healthy Indians ≥50 years, ZOSTAVAX was well tolerated and resulted in expected VZV-specific antibody titer levels at 6 weeks post-vaccination.