Herpes Zoster Risk in Immunocompromised Adults in the United States: A Systematic Review.

BACKGROUND: The primary reported risk factors for herpes zoster (HZ) include increasing age and immunodeficiency, yet estimates of HZ risk by immunocompromising condition have not been well characterized. We undertook a systematic literature review to estimate the HZ risk in immunocompromised patients. METHODS: We systematically reviewed studies that examined the risk of HZ and associated complications in adult patients with hematopoietic cell transplants (HCT), cancer, human immunodeficiency virus (HIV), and solid organ transplant (SOT). We identified studies in PubMed, Embase, Medline, Cochrane, Scopus, and clinicaltrials.gov that presented original data from the United States and were published after 1992. We assessed the risk of bias with Cochrane or Grading of Recommendations Assessment, Development, and Evaluation methods. RESULTS: We identified and screened 3765 records and synthesized 34 studies with low or moderate risks of bias. Most studies that were included (32/34) reported at least 1 estimate of the HZ cumulative incidence (range, 0-41%). There were 12 studies that reported HZ incidences that varied widely within and between immunocompromised populations. Incidence estimates ranged from 9 to 92 HZ cases/1000 patient-years and were highest in HCT, followed by hematologic malignancies, SOT, and solid tumor malignancies, and were lowest in people living with HIV. Among 17 HCT studies, the absence of or use of antiviral prophylaxis at <1 year post-transplant was associated with a higher HZ incidence. CONCLUSIONS: HZ was common among all immunocompromised populations studied, exceeding the expected HZ incidence among immunocompetent adults aged ≥60 years. Better evidence of the incidence of HZ complications and their severity in immunocompromised populations is needed to inform economic and HZ vaccine policies.