NEW ORLEANS, LA—Different dosing schedules for a two-dose candidate herpes zoster (HZ) subunit vaccine (HZ/su) exhibited similar immunogenicity and safety profiles among older adults, authors of a randomized, open-label, phase 3 multicenter Phase 3 study reported at IDWeek 2016.

Scheduling the second dose for month 6 was found to be non-inferior to a previously studied schedule that delivered the second dose of vaccine at month 2.

“HZ/su elicited robust anti-glycoprotein E (gE] immune responses that persisted for up to 12 months post-dose 2 in all study groups,” reported Brecht Geeraerts, PhD, of GSK Vaccines, in Wavre, Belgium, and coauthors. In addition, “HZ/su demonstrated an acceptable reactogenicity and safety profile regardless of the vaccination schedule.”

Previous work had shown that two doses of HZ/su (50 µg varicella-zoster virus [VZV] gE and AS01B Adjuvant System), administered 2 months apart, demonstrated >89% efficacy in preventing HZ among adults age 50 years or older, with a “clinically acceptable” safety profile, the authors noted.

The new study was undertaken to assess the safety and immunogenicity of doses administered at longer intervals.

A total of 354 adults were enrolled in the US and Estonia, and randomly assigned (1:1:1) to be vaccinated at 0 and 2 months (0,2), 0 and 6 months (0,6), or 0 and 12 months (0,12). Blood samples were obtained prior to vaccination and again at months 1 and 12 after the second vaccine dose was administered. Adverse events were recorded at 7 and 30 days after vaccination, and serious adverse events and immune-mediated diseases were recorded throughout the study.

Among 346 participants who completed the study, 343 were included in the analysis as an according-to-protocol immunogenicity-assessment cohort. The mean age for the study groups was 64.5 years in the 0,2-month arm, 64.0 years in the 0,6-month arm, and 64.1 years in the 0,12-month arm. The majority of the patients were female, 75.6%, 64.7%, ad 68.1%, respectively and, with the exception of 3 patients in the 0,2-month arm who were African/African American and 1 in the 0,6-month arm who was “other,” all of the study patients were white or Caucasian/European.

“For both 0,6-month and 0,12-month groups, the predefined success criterion for vaccine response rate was met,” the authors reported. The subsequent non-inferiority for anti-gE immune response geometric mean concentrations versus the 0,2-month schedule was only demonstrated in the 0,6-month arm.

Two participants experienced a fatal adverse event (one from the 0,2-month group and one from the 0,12-month group), but neither these, nor the other reported serious adverse events, were determined to be vaccine-related. The number of subjects reporting serious adverse events from first vaccination until 12 months post-dose 2 was 5 in the 0,2-month arm, 9 in the 0,6-month arm, and 12 in the 0,12-month arm. 

No cases of immune-mediated disease following vaccination were reported.

The incidence of HZ increases from 50 years of age, “presumably due to age-related decline in VZV-specific cellular immunity,” the authors noted.

The study was funded by GlaxoSmithKline Biologicals SA.