Varicella Zoster Vaccine Effective for Hematopoietic Stem Cell Transplant Recipients
Patients receiving auto-HSCT are more susceptible to herpes zoster infections and related complications.
An inactivated varicella zoster vaccine may effectively prevent herpes zoster infections in individuals receiving autologous hematopoietic stem-cell transplants (auto-HSCT) at the peri-transplant period, according to a study published in The Lancet.
Drew J. Winston, MD, of the Department of Medicine at the University of California Los Angeles Medical Center, and associates conducted a randomized, double-blind, placebo-controlled phase 3 clinical trial to assess the effectiveness and safety of inactivated varicella zoster vaccine for patients receiving auto-HSCT.
Patients aged 18 years or older who were scheduled to receive auto-HSCT within 60 days of enrollment or had a history of varicella infection or were seropositive for varicella zoster virus antibodies, or both were eligible for participation. Individuals with a history of herpes zoster within the year of enrollment and/or intended antiviral prophylaxis for longer than 6 months after transplantation were ineligible for participation.
Volunteers were administered either 4 doses of inactivated vaccine (n=560), high-antigen group (n=106), or placebo (n=564); the first dose given 5 to 60 days prior to auto-HSCT and the remaining 3 doses administered approximately 30, 60, and 90 days after transplantation, respectively.
Due to death or participation withdrawal, 44% (n=249) of patients from the vaccine group, 33% (n=35) from the high-antigen group, and 39% (n=200) from the placebo group did not complete the study. In addition, 51 patients were not included in the primary outcome analysis due to lack of vaccination, lack of auto-HSCT, or both.
Average follow-up years for efficacy for vaccine and placebo cohorts were 2.4 years and 2.3 years, respectively; herpes zoster was confirmed in 42 individuals (8%) from the vaccine group and 113 individuals (21%) from the placebo group.
The projected vaccine efficiency was 63.8% with 33% of participants in both the vaccine and placebo groups having serious adverse events (risk difference, 0.2%); serious vaccine-related adverse events were 1% in both groups (risk difference, 0.1%). Individuals in the vaccine cohort experienced more vaccine-related injection-site adverse events than individuals in the placebo cohort (29% vs 7%; risk difference, 22.6%).
“In the future, patients who have been previously excluded from vaccination with the live-virus vaccine might have the opportunity to be immunized with this investigational inactivated virus vaccine,” wrote the authors. “Furthermore, our results provide the rationale for exploring early vaccination strategies for the prevention of infection caused by other pathogens in a growing population of people who have auto-HSCT and other people who are immunosuppressed.”