SAN DIEGO, CA—The investigational inactivated herpes zoster subunit vaccine, HZ/su, was more reactogenic than placebo in the Phase 3 ZOE-50 (Zoster Efficacy Study in Adults Aged 50 Years and Over) study, found authors of a sub-cohort analysis of injection-site and systemic reactions. The findings were reported at IDWeek 2015.

“Both injection site and systemic reactions were more common after HZ/su than after placebo,” reported lead study author Timo Vesikari, MD, PhD, at Tampere Vaccine Research Centre, University of Tampere, in Tampere, Finland, and colleagues. “The antigen and adjuvant could both contribute to the difference.”

Reactogenicity decreased with increasing patient age, the researchers noted.

“All reactions were transient and mostly of mild to moderate intensity,” Dr. Vesikari noted.

Phase 3 study results to date have shown that the HZ/su vaccine, which contains the varicella-zoster virus glycoprotein E and the AS01B Adjuvant System, has a 97.2% vaccine efficacy for the prevention of herpes zoster in adults ≥50 years of age.

In the study, adults were stratified by age (50–59, 60–69, and ≥70 years) and randomly assigned to receive 2 intramuscular doses of HZ/su or saline-solution placebo, 2 months apart.

“Solicited injection site and systemic reactions were recorded for 7 days after each vaccination by a subset of subjects (all subjects ≥70 years of age and randomly selected subjects in the 50–59 and 60–69 years age strata),” Dr. Vesikari and colleagues explained. “Reaction intensity was scored on a scale of 0–3.”

Of 15,411 evaluable subjects who had received at least 1 dose of the study vaccine or placebo, a total of 8,926 were assigned to the reactogenicity subset: 4,460 were administered the HZ/su vaccine and 4,466 were assigned to the placebo group.

In the HZ/su group, injection site reactions occurred in 81.5% (Grade 3, 9.5%) of HZ/su vaccine and 11.9% (Grade 3, 0.4%) of placebo recipients. Systemic reactions occurred in 66.1% (Grade 3, 11.4%) of HZ/su vaccine and 29.5% (Grade 3, 2.4%) of placebo recipients.

The most frequently reported reactions in the HZ/su vaccine group were injection site pain (79.1%, vs. 11.2% in the placebo group); myalgia (46.3% vs. 12.1%); and fatigue (45.9% vs. 16.6%), the coauthors reported.