ORLANDO – An inactivated varicella zoster virus vaccine currently in development for adult patients undergoing autologous hematopoietic stem cell transplantation is efficacious and well tolerated, according to findings from a randomized, placebo-controlled, phase III trial.
During the course of the 2 1/2-year pivotal multicenter trial, confirmed herpes zoster infections occurred in 42 of 560 patients who were randomized to receive inactivated varicella zoster virus vaccine (ZVIN) consistency lot (overall incidence of 32.8 cases/1,000 patient-years), compared with 113 of 564 patients who received placebo (overall incidence of 91.8/1,000 patient-years). The estimated vaccine efficacy was 63.8% after adjusting for age and duration of antiviral prophylaxis,, reported at the combined annual meetings of the Center for International Blood & Marrow Transplant Research and the American Society for Blood and Marrow Transplantation.
The vaccine also was effective for reducing moderate and severe herpes zoster pain (estimated vaccine efficacy, 69.5%), for preventing postherpetic neuralgia (estimated vaccine efficacy, 83.7%), and for prevention of herpes zoster–related complications (estimated vaccine efficacy, 73.5%), he noted.
Study subjects were adults aged 18 years or older who were undergoing autologous hematopoietic stem cell transplantation (auto-HCT) for a malignancy or other indication. The most common underlying diseases were lymphoma and multiple myeloma. All patients had a history of varicella infection or were seropositive for varicella zoster virus (VZV) antibody, and had no history of VZV vaccine or herpes zoster infection within the prior year.
They were randomized to receive a four-dose regimen of either ZVIN consistency lot, ZVIN high-antigen lot, or placebo. A group of 106 patients who received the ZVIN high-antigen lot were included in the safety analysis only. The first ZVIN dose was administered about a month before transplantation, and doses two through four were administered about 30, 60, and 90 days after transplantation. About 90% in each group received antiviral agents after transplantation, and the duration of the use of antivirals also was similar in the groups. All patients were followed for the duration of the study, and those who developed herpes zoster were followed for 6 months after onset.
Herpes zoster cases were confirmed by polymerase chain reaction or by blinded endpoint committee adjudication.
Serious adverse events and vaccine-related serious adverse events occurred in a similar proportion of patients in the treatment and placebo groups (32.9% and 32.7%, and 0.8% and 0.9%, respectively). Vaccine-related events were primarily injection-site reactions. Systemic adverse events that occurred up to 28 days after vaccination were mainly gastrointestinal side effects, such as diarrhea, nausea, and vomiting. Pyrexia, oral mucositis, thrombocytopenia, and febrile neutropenia also were reported.
The most common serious adverse events were infectious complications, such as febrile neutropenia and relapse of underlying disease.
The findings are notable, as patients undergoing auto-HCT have an increased risk of developing herpes zoster infection and its complications, including postherpetic neuralgia, secondary bacterial infections, and disseminated VZV infection, as well as an increased risk of hospitalization and mortality, Dr. Winston explained.
Herpes zoster infections are associated primarily with cell-mediated immunity, and in older studies done prior to the routine use of antiviral prophylaxis, the reported incidence in auto-HCT patients was between 16% and 25%. Because of this high risk, current guidelines call for antiviral prophylaxis during auto-HCT, but even in this current era of acyclovir or valacyclovir prophylaxis, infections occur at relatively high rates after auto-HCT, he noted.
“Now another approach to prevention of herpes zoster infection is vaccination,” he said.
The live attenuated vaccine currently on the market is generally contraindicated in immunocompromised patients – at least in early period after transplantation, but ZVIN showed promise with respect to safety in earlier studies, which led to the current trial.
“This study demonstrated that the inactivated varicella vaccine is very effective for preventing herpes zoster after autologous stem cell transplantation,” Dr. Winston said, noting that efficacy was observed both in those younger than age 50 years and in those aged 50 and older, and also in those who received prophylaxis for less than 3 months and for 3-6 months.
“Finally!” said one audience member, who noted during a discussion of the findings that there has long been a need for a vaccine to prevent herpes zoster in auto-HCT patients.
Dr. Winston reported receiving research funding from Oxford, and serving as a consultant to Merck and Chimerix.