By Stan Deresinski, MD, FACP, FIDSA
Clinical Professor of Medicine, Stanford University
SYNOPSIS: The adjuvanted recombinant zoster vaccine efficacy is high and persistent, with apparent plateauing at > 84% four to six years after vaccination.
SOURCE: Boutry C, Hastie A, Diez-Domingo J, et al. The adjuvanted recombinant zoster vaccine confers long-term protection against herpes zoster: Interim results of an extension study of the pivotal Phase III clinical trials (ZOE-50 and ZOE-70). Clin Infect Dis 2021;Jul 20:ciab629. doi: 10.1093/cid/ciab629.
Boutry et al reported the interim results of a follow-up study of adults older than age 50 years enrolled in two pivotal trials (ZOE-50/70) that demonstrated efficacy in the prevention of herpes zoster in adults by administration of a glycoprotein E-based adjuvanted recombinant vaccine (Shingrix). Patients participating in that study were offered, after approximately five years, entry into this long-term follow-up evaluation, and 7,413 of the original cohort of 14,648 agreed to do so. Vaccine efficacy during the follow-up period, approximately 5.1 to 7.1 years post-vaccination, was 84.0% (95% CI, 75.9-89.8), with an incidence of 8.6 per 1,000 patient-years. The overall efficacy through the entire period after vaccination was 90.9% (95% CI, 88.2-93.2). A plateau of more than 84% efficacy was reached between post-vaccination years 4 and 6. Antibody levels and T cell measures also plateaued at approximately sixfold above prevaccination levels at years 5 to 6.
As pointed out by the authors, Zostavax had lower levels of efficacy than seen with Shingrix in clinical trials and its efficacy diminished rapidly over time. In fact, any efficacy demonstrated with Zostavax was not statistically significant eight years after vaccination of individuals > 60 years of age. In contrast, Shingrix not only provides higher levels of protection, but its efficacy appears to have plateaued at > 84% at four to six years after vaccination.
The follow-up data of Shingrix indicates protection provided is long-lasting and, in fact, modeling of its immunological results suggests the measured responses will persist for at least 20 years post-vaccination. However, it must be recognized that immune correlates of protection remain uncertain. Of importance, though, is that immunosuppressive and immune-modulating therapies were not allowed during the study.