An investigational herpes zoster subunit vaccine (HZ/su) is being evaluated for the prevention of herpes zoster and postherpetic neuralgia in adults 50 years of age or older. A previous trial (Zoster Efficacy Study in Adults 50 Years of Age or Older [ZOE-50]) showed that HZ/su had a vaccine efficacy against herpes zoster of 97.2%, which was consistent across all age groups. Although 24% of the participants in ZOE-50 were 70 years of age or older, the trial was not intended to definitively assess vaccine efficacy against herpes zoster or postherpetic neuralgia in this age group. Therefore, in parallel with ZOE-50, Cunningham et al. conducted a second trial involving only adults who were 70 years of age or older (Zoster Efficacy Study in Adults 70 Years of Age or Older [ZOE-70]) to assess vaccine efficacy against herpes zoster in this population; the authors also estimated vaccine efficacy against postherpetic neuralgia in the combined population (i.e., from ZOE-50 plus ZOE-70) of adults 70 years of age or older and adults 50 years of age or older. The results of this trial can be found in a new Original Article.
• How is the HZ/su vaccine administered?
In the ZOE-70 trial, vaccine or placebo (0.9% saline solution) was administered (0.5 ml) into the deltoid muscle at month 0 and month 2.
• What is the efficacy of the HZ/su vaccine among adults 70 years of age and older?
In the ZOE-70 total vaccinated cohort, 432 suspected episodes of herpes zoster were reported, 270 of which were confirmed as herpes zoster. Of the 270 confirmed cases, 246 occurred in the modified vaccinated cohort (the primary cohort for the efficacy analysis): 23 in HZ/su recipients and 223 in placebo recipients, after a mean follow-up period of 3.7 years. The incidence of herpes zoster per 1000 person-years was 0.9 in the HZ/su group and 9.2 in the placebo group, for an overall vaccine efficacy of 89.8% (95% confidence interval [CI], 84.2 to 93.7; P<0.001). In the pooled analysis of participants 70 years of age or older from ZOE-70 and ZOE-50, a total of 25 confirmed cases of herpes zoster occurred in HZ/su recipients, as compared with 284 cases in placebo recipients, which resulted in a vaccine efficacy of 91.3% against herpes zoster (95% CI, 86.8 to 94.5%).
Morning Report Questions
Q: Is the efficacy of HZ/su different for those between 70 and 79 years of age as compared to those 80 years of age or older?
A: Vaccine efficacy against herpes zoster in the pooled analysis was very similar in the two age groups studied (91.3% among participants 70 to 79 years of age and 91.4% among participants ≥80 years of age), which indicated that there was no decline in efficacy with age. This finding is consistent with the results of ZOE-50, in which vaccine efficacy against herpes zoster was found to be similar in all age groups (50 to 59, 60 to 69, and ≥70 years of age), but it contrasts with the efficacy of the approved live attenuated vaccine (Zostavax), which was found to decline with increasing age: 70% in adults 50 to 59 years of age, 64% in adults 60 to 69 years of age, 41% in adults 70 to 79 years of age, and 18% in adults 80 years of age or older.
Q: How does the HZ/su vaccine affect rates of postherpetic neuralgia?
A: In the analyses by Cunningham et al., the incidence of postherpetic neuralgia among HZ/su recipients with breakthrough herpes zoster did not differ significantly from that among placebo recipients (12.5% and 9.6%, respectively; P=0.54). Protection against postherpetic neuralgia appeared to be driven by the lower incidence of herpes zoster (91.3% vaccine efficacy against herpes zoster vs. 88.8% vaccine efficacy against postherpetic neuralgia in the pooled population of adults ≥70 years of age); there is no evidence for additional efficacy against postherpetic neuralgia among HZ/su recipients with breakthrough herpes zoster.